Fuel cell system and exhaust gas humidity inference method thereof

Abstract

Provided is a fuel cell system capable of obtaining the humidity of exhaust-side air useful for the state management of a fuel cell with a simple structure, and a method of estimating the exhaust humidity. A fuel cell system of one embodiment of the present application includes a mass flow rate value measurement unit that measures the mass flow rate value WF1 of intake-side air and the mass flow rate value WF2 of exhaust-side air; a consumed oxygen mass flow rate value acquisition unit that acquires the mass flow rate value Ow of consumed oxygen consumed in a fuel cell; an exhaust temperature acquisition unit that acquires the temperature value Tout of exhaust-side air; and an exhaust humidity estimation unit that estimates the humidity Hout of exhaust-side air, wherein the exhaust humidity estimation unit estimates the humidity Hout of exhaust-side air on the basis of the difference between the intake flow rate and the exhaust flow rate of the fuel cell system and the mass flow rate value of consumed oxygen.

Description

TECHNICAL FIELD

[0001] The present application relates to a fuel cell system suitable for use in, for example, a vehicle, and more particularly, to a technique for accurately estimating exhaust humidity with a simple method. BACKGROUND

[0002] In modern society, for example, automobiles are indispensable as a means of transportation, and various vehicles travel on the road in daily life. In recent years, as a new battery that can replace lead storage batteries and / or lithium ion batteries, a fuel cell that has a smaller load on the environment has attracted attention.

[0003] In such a fuel cell, electric power is obtained by supplying hydrogen to one electrode (fuel electrode) and supplying oxygen to the other electrode (air electrode) and causing them to react. Here, a solid electrolyte is used in the fuel cell, and it is important to manage the moisture of the solid electrolyte.

[0004] PRIOR ART DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-305700 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Not limited to the above-described patent documents, the current technology cannot be said to appropriately meet the needs of the market, and the following problems exist.

[0008] For example, in the above-described patent document 1, the humidity of air flowing through the intake (air supply path) of the fuel cell is estimated from the temperature in the vicinity of the humidifier provided near the inlet of the fuel cell and the temperature in the fuel cell, thereby ensuring power generation performance.

[0009] However, the humidity of the air on the outlet side of the fuel cell contains moisture generated along with power generation, so it is expected that the humidity values will be different on the air supply path side and the air discharge path side of the fuel cell.

[0010] Furthermore, since the management of the state of the fuel cell is also a key factor in the management of the moisture of the electrolyte, there are cases where the humidity of the exhaust path through the electrolyte is better.

[0011] The present application was made in view of the above-described problems as an example, and aims to provide a fuel cell system capable of obtaining an exhaust humidity useful for the management of the state of the fuel cell with a simple structure, and a method of estimating the exhaust humidity.

[0012] TECHNICAL SOLUTION

[0013] To address the aforementioned issues, a fuel cell system (1) in one embodiment of the present invention generates electricity using the reaction of oxygen and hydrogen, comprising: a mass flow rate measurement unit that measures the mass flow rate WF1 of the inlet air of the fuel cell and the mass flow rate WF2 of the exhaust air of the fuel cell; a mass flow rate acquisition unit that acquires the mass flow rate Ow of the oxygen consumed in the fuel cell; an exhaust temperature acquisition unit that acquires the temperature Tout of the exhaust air; and an exhaust humidity inference unit that infers the humidity Hout of the exhaust air, the exhaust humidity inference unit inferring the humidity Hout of the exhaust air based on the difference between the inlet flow rate and the exhaust flow rate of the fuel cell system and the mass flow rate of the oxygen consumed.

[0014] It should be noted that in the fuel cell system described in (1) above, preferably (2) the exhaust humidity inference unit calculates the flow rate WVout of the water vapor in the exhaust side air based on the formula WF2-(WF1-Ow) above, and infers the humidity Hout of the exhaust side air based on the ratio of the calculated water vapor flow rate WVout to the saturated water vapor amount of the exhaust side air corresponding to Tout above.

[0015] In addition, in the fuel cell system described in (1) or (2) above, preferably (3) the fuel cell system further includes a battery temperature acquisition unit for acquiring the temperature of the fuel cell, and the exhaust humidity inference unit determines the flow rate of water vapor contained in the intake air based on the temperature acquired by the battery temperature acquisition unit.

[0016] In addition, in any one of the fuel cell systems described in (1) to (3) above, preferably (4) the fuel cell system further includes an intake side humidity measuring unit that measures the amount of water vapor in the intake side air, and the exhaust humidity inference unit subtracts the flow rate of water vapor contained in the intake side air from the mass flow rate value WF1 based on the amount of water vapor measured by the intake side humidity measuring unit.

[0017] In addition, in any one of the fuel cell systems (1) to (4) above, preferably (5) the fuel cell system includes: a first mass flow sensor disposed on the inlet side of the fuel cell to measure the mass flow value WF1; and a second mass flow sensor disposed on the exhaust side of the fuel cell to measure the mass flow value WF2.

[0018] In addition, to solve the above-mentioned problems, the exhaust humidity estimation method (6) of the fuel cell system in one embodiment of the present invention is an exhaust humidity estimation method of the fuel cell system for estimating the humidity of the exhaust side air of the fuel cell, including: a mass flow rate value acquisition step, which acquires the mass flow rate value WF1 of the intake side air of the fuel cell and the mass flow rate value WF2 of the exhaust side air of the fuel cell respectively; a mass flow rate value acquisition step, which acquires the mass flow rate value Ow of the consumed oxygen in the fuel cell; an exhaust temperature acquisition step, which acquires the temperature value Tout of the exhaust side air; and an exhaust side humidity estimation step, which infers the humidity Hout of the exhaust side air based on the difference between the intake flow rate and the exhaust flow rate of the fuel cell system and the mass flow rate value of the consumed oxygen.

[0019] In addition, in the exhaust humidity estimation method described in (6) above, it is preferable that (7) in the exhaust humidity estimation step, the flow rate WVout of water vapor in the exhaust air is calculated based on the mass flow rate WF2 - (the mass flow rate WF1 - the mass flow rate Ow of oxygen consumption), and the humidity Hout of the exhaust air is estimated based on the ratio of the calculated water vapor flow rate WVout to the saturated water vapor amount of the exhaust air corresponding to Tout.

[0020] In addition, in the exhaust humidity estimation method described in (6) or (7) above, it is preferable that (8) the exhaust humidity estimation process further includes a battery temperature acquisition process for obtaining the temperature of the fuel cell, and the flow rate of water vapor contained in the intake air is determined based on the obtained temperature.

[0021] In addition, in any one of the exhaust humidity estimation methods (6) to (8) above, it is preferable that the exhaust humidity estimation step (9) further includes an intake humidity measurement step for measuring the amount of water vapor in the intake air, and the amount of water vapor contained in the intake air is subtracted from the mass flow rate value WF1 based on the measured amount of water vapor.

[0022] In addition, in any one of the exhaust humidity estimation methods (6) to (9) above, it is preferable to (10) use a first mass flow sensor disposed on the intake side of the fuel cell and a second mass flow sensor disposed on the exhaust side of the fuel cell to measure the mass flow value WF1 and the mass flow value WF2 respectively.

[0023] Technical effect

[0024] According to the present invention, the humidity of the exhaust-side air can be obtained with a simple structure. Attached Figure Description

[0025] Figure 1 is a whole block diagram of a fuel cell system of one embodiment.

[0026] Figure 2 is a block diagram of a control device (ECU) of one embodiment.

[0027] Figure 3 is a flowchart showing an exhaust gas humidity estimation method of one embodiment.

[0028] Figure 4 is a flowchart showing an example of humidity estimation in the flowchart of Figure 3

[0029] Figure 5 is a flowchart showing another example of humidity estimation in the flowchart of Figure 3

[0030] Figure 6 is a whole block diagram of a fuel cell system of a modified example.

[0031] Symbol explanation

[0032] 100: control system

[0033] 10: control device

[0034] 20: fuel cell

[0035] 30: gas supply system DETAILED DESCRIPTION

[0036] Next, a preferred embodiment for implementing the present application will be described. In addition, with respect to the structure other than the following detailed description, elements technology and / or structure related to the known fuel cell system including the above-described patent document can be appropriately supplemented.

[0037] <Fuel cell system 100>

[0038] First, with reference to Figure 1 The structure of the fuel cell system 100 in the preferred embodiment of the present application will be described. The fuel cell system 100 in the present embodiment is mounted on a fuel cell vehicle (FCV), for example. Hereinafter, as an application example of the fuel cell system 100, the case of the FCV will be described, but the present application is not limited to the FCV, and is also suitable for a stationary type battery system such as a residential device and / or a mobile type battery system such as an airplane.

[0039] The fuel cell system 100 mounted on the FCV is configured to include: a control device 10 (ECU) that controls each part of the vehicle; a fuel cell 20 that is controlled by the control device 10; and a gas supply system 30 that supplies anode gas and cathode gas to the fuel cell 20. ​​

[0040] In the present embodiment, the air supply system 30 is configured to include an air filter 31 as a cathode gas supply unit that supplies air to the cathode electrode side of the fuel cell 20, a hydrogen tank 33 that supplies hydrogen to the anode electrode side, and the like.

[0041] As shown in FIG. 1, air taken in from the outside of the vehicle via the air filter 31 is compressed by the compressor 32 and is sent to the oxygen electrode 21 (air electrode) of the fuel cell 20 via the air supply path. At this time, humidification is preferably performed by a known humidification device (not shown). Figure 1

[0042] Then, after the oxygen is consumed by the electrochemical reaction within the fuel cell 20, the air is exhausted to the outside of the system via the exhaust path while adjusting the pressure with the air pressure adjusting valve 18a.

[0043] Note that the pressure of the air supplied to the oxygen electrode 21 is detected by a known air pressure gauge (not shown) provided near the inlet of the oxygen electrode 21 in the fuel cell 20, and the air pressure adjusting valve 18a is controlled by the control device 10 in such a manner that the detected air pressure reaches a predetermined pressure.

[0044] In addition, as a method of humidifying the air supplied to the fuel cell 20, a method using a water vapor exchange film that reuses moisture in the exhausted air and / or a film humidifier and / or a known various devices such as a sprayer that supply moisture such as pure water to the air can be used.

[0045] In addition, the fuel cell system 100 of the present embodiment has a mass flow sensor 11a as a mass flow value measuring unit that measures the mass flow of the intake-side air supplied to the fuel cell 20 on the supply path of the intake-side air. More specifically, in the present embodiment, the mass flow sensor 11a is preferably provided on the above-described supply path at a position that is located on the upstream side of the compressor 32 and is located on the downstream side of the air filter 31.

[0046] In addition, the fuel cell system 100 of the present embodiment can have a humidity sensor 15a as an intake-side humidity measuring unit that measures the humidity, i.e., the amount of water vapor (moisture amount), of the intake-side air supplied to the fuel cell 20 on the supply path of the intake-side air. Note that the humidity sensor 15a is not necessarily required and can be appropriately omitted under predetermined conditions described later.

[0047] ​On the other hand, the fuel cell system 100 of this embodiment has a mass flow sensor 11b as a mass flow measurement unit for measuring the mass flow rate of the exhaust air (exhaust air) discharged from the fuel cell 20 in the exhaust path. More specifically, in this embodiment, the mass flow sensor 11b is preferably provided on the upstream side of the specific air pressure regulating valve 18a in the aforementioned exhaust path. These mass flow sensors 11a and 11b can be suitable for FCVs among various known mass flow sensors such as Coriolis flow meters and / or thermal mass flow meters.

[0048] Furthermore, the fuel cell system 100 of this embodiment preferably includes a temperature sensor 13a, which serves as an exhaust temperature measuring unit for measuring the temperature of the exhaust air, in the exhaust path of the exhaust-side air (exhaust air) discharged from the fuel cell 20. It should be noted that the temperature sensor 13a is not essential and can be appropriately omitted under predetermined conditions described later.

[0049] like Figure 1 As shown, the hydrogen supplied through the hydrogen tank 33 is delivered to the hydrogen electrode 22 (fuel electrode) of the fuel cell 20 after passing through the hydrogen supply path and having its pressure regulated to the desired pressure by the hydrogen pressure regulating valve 34. This hydrogen electrode 22 is positioned opposite the oxygen electrode 21 via an electrolyte membrane 23, for example, using a solid polymer electrolyte membrane. The hydrogen supplied to the hydrogen electrode can also be humidified using a known humidifier (not shown). It should be noted that in the hydrogen supply system of this embodiment, since nitrogen and / or impurities contained in the hydrogen tank 33 that permeate from the oxygen electrode 21 to the hydrogen electrode 22 during power generation accumulate, it is preferable to have a path and a discharge valve 37 for discharging these impurities outside the system.

[0050] Furthermore, any additional hydrogen supplied to the hydrogen electrode 22 after hydrogen has been consumed in the electrochemical reaction within the fuel cell 20 is reused via a hydrogen circulation path and through a hydrogen recirculator 35 back to the hydrogen supply path. The pressure of the hydrogen supplied to the hydrogen electrode 22 is detected by a pressure gauge 36 located near the inlet of the hydrogen electrode 22, and the hydrogen pressure regulating valve 34 is controlled by the control device 10 to bring the detected hydrogen pressure to a predetermined pressure. It should be noted that, for example, such a hydrogen pressure regulating unit could be implemented by using the vehicle's ECU to control the hydrogen injection quantity of the injector to achieve the aforementioned predetermined pressure, or by using the hydrogen pressure regulating valve 34 to mechanically control the pressure of the hydrogen injection quantity of the injector.

[0051] In addition, a cooling water system is provided to maintain the battery body at an appropriate temperature by cooling the heat generated by the power generation through the fuel cell 20. More specifically, cooling water (coolant) pressurized and delivered by the cooling water pump 25 absorbs the aforementioned heat by passing it through the fuel cell 20, and is then transported to a heat exchanger 24, such as a radiator, via a cooling water circulation path. The heat is then discharged outside the system through the heat exchanger 24, and the cooling water is then pressurized back into the fuel cell 20 by the cooling water pump 25 for circulation.

[0052] It should be noted that the fuel cell system 100 of this embodiment includes a thermometer 13b for detecting the temperature of the cooling water discharged from the fuel cell 20. Therefore, the control device 10 monitors the temperature of the cooling water passing through the fuel cell 20 using this thermometer 13b while simultaneously adjusting the temperature T of the fuel cell 20. fcv The adjustment is for controlling the temperature suitable for power generation.

[0053] As a load device that consumes the electricity generated by the fuel cell 20, an inverter device that supplies electricity to the drive motor of the FCV can be exemplified. The voltage generated by the fuel cell 20 is detected using a voltmeter (not shown), and the current supplied from the fuel cell 20 to the inverter device, etc., is detected using an ammeter 12a.

[0054] [Control Device 10]

[0055] Next, refer to Figure 2 The structure of the control device 10 in the fuel cell system 100 of this embodiment will be described.

[0056] like Figure 2 As shown, the control device 10 of this embodiment is configured to include: a mass flow rate measuring unit 11, an oxygen consumption mass flow rate acquiring unit 12, an exhaust-side air temperature acquiring unit 13, a saturated water vapor acquiring unit 14, an intake-side water vapor acquiring unit 15, an exhaust-side air humidity inference unit 16, and a notification control unit 17. As this control device 10, a known computer device such as a CPU with a memory (not shown) can be used as an example, which has the function of controlling the entire fuel cell system 100 described above.

[0057] Furthermore, as shown in the figure, the control device 10 is preferably configured to be connected to an external network such as the Internet via the communication device 40. Such a communication device 40 can be exemplified by a known in-vehicle communication device capable of communicating with the external network of the FCV. Additionally, the external network is not limited to the Internet, but also includes information communication networks from base stations that transmit various information such as traffic jam information and / or road traffic information via wireless communication.

[0058] In addition, the control device 10 is configured to be able to receive various signals from sensors 50 mounted on the FCV. These sensors 50 are mounted on the FCV and have various functions of detecting various information. In the present embodiment, as an example, a humidity sensor 51 and an outside air temperature sensor 52, and the like can be exemplified, but a publicly known sensor mounted on a vehicle, such as an illuminance sensor and / or a road surface sensor, and the like can be used. In addition, the control device 10 is configured to be able to communicate with a publicly known navigation device 60, a speaker SP, and a display DP, each of which is mounted on the FCV.

[0059] Note that, in the present embodiment, the humidity sensor 51 and the outside air temperature sensor 52 are illustrated, but these publicly known sensors can be appropriately selected to be omitted in order to exert a desired function.

[0060] The mass flow rate value measuring section 11 has a function as a mass flow rate value measuring unit that measures the mass flow rate value WF1 of the intake side air of the fuel cell 20 and the mass flow rate value WF2 of the exhaust side air of the fuel cell 20, respectively. More specifically, the mass flow rate value measuring section 11 acquires the mass flow rate value WF1 of the intake side air from a mass flow rate sensor 11a (first mass flow rate sensor) that is electrically connected to the control device 10, and similarly acquires the mass flow rate value WF2 of the exhaust side air from a mass flow rate sensor 11b (second mass flow rate sensor) that is electrically connected to the control device 10.

[0061] Note that, in the present embodiment, the mass flow rate value is directly measured using the mass flow rate sensors, but it can be a manner in which, for example, a publicly known volume flow rate sensor is used to measure a volume flow rate value, and then the volume flow rate value is converted into a mass flow rate value by a publicly known method. In this way, at least one of the mass flow rate sensor 11a and the mass flow rate sensor 11b can be replaced with a publicly known volume flow rate sensor.

[0062] The consumed oxygen mass flow rate value acquiring section 12 has a function as a consumed oxygen mass flow rate value acquiring unit that acquires a consumed oxygen mass flow rate value Ow consumed in the fuel cell 20 due to power generation. More specifically, in the present embodiment, the consumed oxygen mass flow rate value acquiring section 12 calculates the consumed oxygen mass flow rate value Ow on the basis of a current value measured by a current meter 12a that is electrically connected to the control device 10. In the present embodiment, a theoretical formula "4H +The oxygen consumption mass flow rate value Ow is calculated from the formula: + O2+ 4e→ 2H2O". It should be noted that the oxygen consumption mass flow rate value Ow can also be calculated in advance by experiment or simulation of the relationship between the oxygen and hydrogen consumed in the fuel cell 20 for power generation and the electric energy (charge amount) and held. Then, based on the held relationship and the current density and the effective reaction area, the oxygen consumption mass flow rate value is calculated from the charge amount (coulomb (C) = current value (A) x second (s)) by a known method.

[0063] The exhaust side air temperature acquisition section 13 has a function as an exhaust temperature acquisition unit that acquires the temperature value Tout of the exhaust side air of the fuel cell 20 described above. More specifically, the exhaust side air temperature acquisition section 13 can acquire the temperature value Tout of the exhaust side air measured by the temperature sensor 13a disposed on the exhaust path described above.

[0064] In addition, in the case where the fuel cell system 100 does not have the temperature sensor 13a described above, the temperature value Tout of the exhaust side air can be replaced with the temperature value of the thermometer 13b that detects the temperature of the cooling water discharged from the fuel cell 20. Because the temperature of the cooling water immediately after being discharged from the fuel cell 20 can be regarded as equivalent to the temperature of the exhaust side air.

[0065] The saturated water vapor amount acquisition section 14 has a function of acquiring the saturated water vapor amount at a predetermined temperature from the saturated water vapor curve data held in advance in the memory M electrically connected to the control device 10. It should be noted that the saturated water vapor curve data held in the memory M, such as the relationship between the saturated water vapor amount and the air temperature (temperature), is set based on a known conversion formula such as Tetens' formula and / or Wagner's formula.

[0066] The intake side water vapor amount acquisition section 15 has a function as an intake side humidity measurement unit that acquires the water vapor amount (moisture amount) contained in the intake side air supplied to the fuel cell 20. More specifically, the intake side water vapor amount acquisition section 15 is configured to acquire the water vapor amount (moisture amount) measured by the humidity sensor 15a disposed on the supply path of the fuel cell 20 described above.

[0067] The exhaust side air humidity inference section 16 has a function as an exhaust humidity inference unit that infers the humidity Hout of the exhaust side air based on the difference between the intake flow rate and the exhaust flow rate in the fuel cell system 100 and the oxygen consumption mass flow rate value Ow described above. More specifically, as an example, the exhaust side air humidity inference section 16 of the present embodiment can perform the processes of a to g shown below.

[0068] α: subtracts the value of the mass flow rate of consumed oxygen Ow from the mass flow rate value WF1 of the intake side air, from the mass flow rate value WF2 of the exhaust side air described above. The flow rate WVout of water vapor in the exhaust side air is thus calculated.

[0069] β: acquires the saturated water vapor amount a(T)out of the exhaust side air corresponding to the acquired temperature value Tout of the exhaust side air.

[0070] γ: infers the humidity Hout of the exhaust side air based on the ratio (WVout / a(T)out) of the flow rate WVout of water vapor in the exhaust side air to the saturated water vapor amount a(T)out of the exhaust side air.

[0071] Note that at this time, the exhaust side air humidity inference unit 16 can determine the amount (mass flow rate) of water vapor (moisture) contained in the intake side air based on the temperature T fcv of the fuel cell 20.

[0072] In addition, when the fuel cell system 100 is provided with the intake side humidity measurement unit (humidity sensor 15a) described above, the exhaust side air humidity inference unit 16 subtracts the flow rate of water vapor contained in the intake side air from the mass flow rate value WF1 based on the humidity measured by the intake side humidity measurement unit described above.

[0073] The notification control unit 17 has a function of controlling notification via the speaker SP and the display DP described above. For example, the notification control unit 17 can notify the state of the fuel cell 20 via the speaker SP or the display DP based on the inference result of the humidity Hout of the exhaust side air obtained by the exhaust side air humidity inference unit 16. Thus, in the case where a failure of the fuel cell 20 is detected based on the inference result of the humidity Hout, it is possible to quickly convey the abnormality to the occupant or the like.

[0074] In addition, the inference result of the humidity Hout of the exhaust side air by the exhaust side air humidity inference unit 16 can be utilized in the state control of the FCV provided with the fuel cell system 100. For example, humidification control can be performed at the intake side in the case where the humidity Hout described above is low, and drying control can be performed conversely in the case where the humidity Hout is high. As specific methods of these humidification control and / or drying control, for example, control of the temperature rise / decrease and / or intake flow rate, supercharging pressure, and the like in the fuel cell 20 can be exemplified.

[0075] <Exhaust Humidity Inference Method>

[0076] Next, appropriate reference will be made to Figures 3-5 The exhaust humidity inference method of the fuel cell system 100 in the present embodiment will be described.

[0077] As shown in FIG. 1, first, in step 1, it is determined whether or not the humidity of the exhaust-side air of the fuel cell 20 is to be estimated. In the case where it is determined in step 1 that the humidity estimation is required, the process proceeds to step 2, but the determination of whether or not the humidity estimation is required can be performed automatically at every predetermined period, or the input of whether or not the humidity estimation is required can be performed manually by the occupant or the like. Figure 3

[0078] In the subsequent step 2, it is determined whether or not the fuel cell 20 is stable. Then, in the case where the state after a lapse of a certain period of time after the start of the fuel cell system 100 is stable, the process proceeds to step 3-A, whereas in the case where the state after the start of the fuel cell system 100 is unstable, the process proceeds to step 3-B. Then, in step 3-B, a warning display such as that the humidity estimation is currently impossible is performed via the display DP described above.

[0079] Note that, since the humidity in the state after the start of the fuel cell system 100 is sometimes also estimated, this step 2 is not necessarily required and can be appropriately omitted.

[0080] [Humidity Estimation Process (One)] In step 3-A, in order to perform the state management of the fuel cell 20, the humidity estimation process of the exhaust-side air shown in FIG. 3, for example, is performed by the control device 10 described above. Figure 4

[0081] That is, as shown in FIG. 3, in the humidity estimation process, first, in step 31, the moisture amount in the intake-side air (intake-side humidity measurement process) is measured. More specifically, the moisture amount in the intake-side air is measured on the basis of the humidity measured by the humidity sensor 15a as the intake-side humidity measurement unit described above. Figure 4

[0082] Then, in this humidity estimation process (one), when the humidity of the exhaust-side air is estimated, the value obtained by subtracting the flow rate value of the water vapor contained in the intake-side air (the moisture amount in the intake-side air) from the value of the mass flow rate value WFl measured by the mass flow rate sensor 11a is the "mass flow rate value WFl of the intake-side air". Note that, as shown in the humidity estimation process (two) described later, the flow rate value of the water vapor described above (the moisture amount in the intake-side air) can be included in the "mass flow rate value WFl of the intake-side air", and, for example, in the case where the fuel cell is sufficiently high in temperature, or the like, it can be processed as a value without the flow rate value of the water vapor (dry value).

[0083] ​​​Next, in step 32, the mass flow rate value WF1 of the air on the intake side of the fuel cell 20 and the mass flow rate value WF2 of the air on the exhaust side of the fuel cell 20 are acquired respectively via the above-described mass flow rate sensors 11a and 11b (mass flow rate value acquisition process).

[0084] Then, in a subsequent step 33, the mass flow rate value Ow of the consumed oxygen in the fuel cell 20 is acquired on the basis of the current value measured by the ammeter 12a as the above-described consumed oxygen mass flow rate value acquisition unit (consumed oxygen mass flow rate value acquisition process).

[0085] Then, in subsequent steps 34 to 36, using the respective parameters obtained above, the humidity of the air on the exhaust side is inferred on the basis of the difference between the intake flow rate and the exhaust flow rate of the fuel cell system 100 and the mass flow rate value Ow of the consumed oxygen (exhaust side humidity inference process).

[0086] That is, in step 34, the flow rate WVout of the water vapor in the air on the exhaust side is calculated on the basis of "the mass flow rate value WF2 - (the above-described mass flow rate value WF1 - the above-described consumed oxygen mass flow rate value Ow)".

[0087] In addition, in step 35, the temperature value Tout of the air on the exhaust side is acquired by the temperature sensor 13a as the exhaust temperature acquisition unit (exhaust temperature acquisition process), and the saturated water vapor amount corresponding to this temperature value Tout of the air on the exhaust side is read out and acquired from the memory M.

[0088] Then, in step 36, the humidity Hout of the air on the exhaust side is inferred on the basis of the ratio (WVout / a(T)out) of the above-described saturated water vapor amount a(T)out of the air on the exhaust side to the flow rate WVout of the water vapor in the air on the exhaust side.

[0089] Hereinafter, one example of applying the above-described exhaust humidity inference method to an actual vehicle will be shown.

[0090] That is, it is assumed that the FCV equipped with the fuel cell system 100 of the present embodiment performs the state management of the fuel cell 20 in a certain scene while running. At this time, the parameter values measured by the respective sensors above respectively represent the following values.

[0091] (a) The mass flow rate value WF1 acquired by the mass flow rate sensor 11a: 100 g / sec

[0092] (b) The mass flow rate value WF2 acquired by the mass flow rate sensor 11b: 110 g / sec

[0093] (c) The consumed oxygen mass flow rate value Ow derived from the current value of the ammeter 12a: 10 g / sec

[0094] (d) Temperature value Tout measured by temperature sensor 13a: 90°C

[0095] (e) Amount of moisture in intake-side air measured by humidity sensor 15a: 0.3 g / sec

[0096] (f) Temperature T of fuel cell 20 fcv : 90°C

[0097] First, a value obtained by subtracting the mass flow rate of water vapor from the mass flow rate of intake-side air is calculated as a mass flow rate value WF1. Then, the amount of water vapor contained in the intake-side air is subtracted from the mass flow rate value WF1 based on the amount of water vapor measured by humidity sensor 15a. Thus, the mass flow rate value WF1 = 100 - 0.3 = 99.7 g / sec is obtained by subtracting the mass flow rate portion of water vapor.

[0098] Next, the flow rate WVout of water vapor in exhaust-side air is calculated as "20.3 g / sec" by "110 - 99.7 + 10" based on "mass flow rate value WF2 - (above mass flow rate value WF1 - above mass flow rate value Ow of consumed oxygen)".

[0099] Next, the saturated water vapor amount corresponding to the temperature value Tout (90°C) (421.45 g / m 3 in this case) is read out from memory M.

[0100] Here, the gas composition of exhaust-side air is "nitrogen: 100 x 0.8 / 28 = 2.9 mol, oxygen: (100 x 0.2 - 10) / 32 = 0.3 mol". In addition, the number of moles of water vapor calculated above is "20.3 / 18 = 1.1 mol".

[0101] Therefore, at the exhaust pressure (inferred from the measured value or the boost pressure) 240 kPa (absolute pressure), the volumetric flow rate of exhaust-side air becomes the following equation (K) using PV = nRT.

[0102] 240 x (volumetric flow rate of exhaust-side air) = (2.9 + 0.3 + 1.1) x 8.31 x 10 -3 x (90 + 273)...(K)

[0103] Therefore, as a value of (volumetric flow rate of exhaust-side air), 0.054 m 3 / sec is calculated. Here, because exhaust humidity [%] = water vapor flow rate [g / sec] / flow rate of exhaust-side air [m 3 / sec] / saturated water vapor amount [g / m 3 ​​​​​​​​​​​​​​​​​​​​​​​Hout= 20 / 0.054 / 421.45 x 100 = 87.8 (%)...(L)

[0104] Hout= 20 / 0.054 / 421.45 x 100 = 87.8 (%)...(L)

[0105] [Humidity estimation process (two)] Next, referring to Figure 5 Another example of the humidity estimation process in the present embodiment will be described. Note that in the present example, the same reference signs and the like are affixed to the same contents as those of the already described "humidity estimation process (one)", and the description thereof is appropriately omitted.

[0106] As Figure 5 indicated, in the humidity estimation process (two) of the present embodiment, there is a feature of treating the intake-side air as dry air (almost zero moisture content) in the case where the cell temperature of the fuel cell 20 is sufficiently high. Here, the "case where the cell temperature is sufficiently high" means a case where the moisture content in the air does not affect the estimation of the humidity Houtof the exhaust-side air described above, and can be set to 80°C or higher, for example.

[0107] That is, in the humidity estimation process (two), first, as step 30, the temperature T fcv of the fuel cell 20 is acquired by the thermometer 13c Figure 1 ), and it is determined whether or not the cell temperature is a predetermined value or higher (cell temperature acquisition process). As described above, in the present embodiment, as the "predetermined value", 80°C can be set. Note that as the cell temperature acquisition unit that acquires the temperature T fcv of the fuel cell 20, there is no particular limitation, and various thermometers known to be mountable on a fuel cell can be used.

[0108] Then, in step 30, in the case where the temperature T fcv of the fuel cell 20 is not the predetermined value or higher (NO in step 30), the process proceeds to step 31A to measure the moisture content in the intake-side air. Note that because this step 31A is the same as the above-described step 31, the description thereof is omitted.

[0109] On the other hand, in step 30, in the case where the temperature T fcv of the fuel cell 20 is the predetermined value or higher (YES in step 30), the process proceeds to step 31B to perform a setting process of treating the intake-side air as dry air (i.e., moisture content is zero). Thus, in step 31B, the flow rate of the water vapor contained in the intake-side air is determined on the basis of the acquired temperature T fcv of the fuel cell 20.

[0110] After that, the same processing as the humidity estimation processing (one) is performed except that the amount of moisture in the intake-side air is zero.

[0111] Thus, in the humidity estimation processing (two), because the state around the fuel cell 20 at a high temperature is low in the amount of moisture, the intake-side air flowing into such a fuel cell 20 is treated as dry gas. Thereby, compared with the humidity estimation processing (one), the humidity Hout of the exhaust-side air can be estimated in a simpler method.

[0112] According to the fuel cell system and the exhaust humidity estimation method of the above-described embodiment, if it is a normal FCV, the humidity of the exhaust-side air can be easily obtained using only the standard components equipped.

[0113] Note that the above-described embodiments are one example of a preferred aspect of the present application, and as long as the gist of the present application is not deviated from, the elements of the embodiments can be appropriately combined to realize a new configuration and / or control. Hereinafter, a modification example applicable to the above-described embodiments will be described.

[0114] <Modification Example>

[0115] Figure 6 The modification example of the above-described embodiment is shown.

[0116] As shown in the figure, the fuel cell system 110 of the modification example is characterized in that, compared with the above-described fuel cell system 100, at least the mass flow sensor 1 lb is omitted from the exhaust path. That is, in the present modification example, it is characterized in that the mass flow sensor 1 lb is replaced with the temperature meter 13b, the air pressure adjusting valve 18a, and the exhaust-side pressure sensor 19a originally equipped in the FCV.

[0117] More specifically, as for the temperature of the exhaust-side air, as described above, the temperature value of the temperature meter 13b that detects the temperature of the cooling water discharged from the fuel cell 20 is used for the calculation. Then, the control device 10 further acquires the opening degree of the above-described air pressure adjusting valve 18a and the pressure acquired by the exhaust-side pressure sensor 19a, and, for example, as disclosed in Japanese Patent Application Publication No. 2007-172971, the mass flow value WF2 of the exhaust-side air is calculated using a known conversion formula.

[0118] Thus, according to the present modification example, in addition to the effects of the above-described embodiment, it is possible to further reduce the number of components without equipping a dedicated component for estimating the humidity of the exhaust-side air.

[0119] In addition, in the above-described humidity estimation process, as an alternative to the humidity estimation process (one) in which the humidity of the actual intake-side air is measured using the above-described humidity sensor 15a, a humidity estimation process (two) is described, but the present application is not limited to this example. As another alternative, for example, the humidity of the intake-side air can also be set in advance to a provisional value (for example, 50% or the like) and handled as a provisional fixed value, or the position information of the vehicle and the date and time information and weather information can be acquired to predict the humidity of the intake-side air according to at least one of the season, weather, and time zone of the region.

[0120] The preferred embodiments and modifications of the present application have been described in detail above with reference to the drawings, but the present application is not limited to such examples. Various modifications or changes that can be conceived by those having ordinary knowledge in the technical field to which the present application pertains within the scope of the technical idea recited in the claims will be apparent, and these certainly also belong to the technical scope of the present application.

Claims

1. A fuel cell system, characterized in that, Generating electricity using the reaction of oxygen and hydrogen includes: The mass flow rate measurement unit measures the mass flow rate WF1 of the air intake side of the fuel cell and the mass flow rate WF2 of the air exhaust side of the fuel cell, respectively. The oxygen consumption mass flow rate acquisition unit acquires the oxygen consumption mass flow rate Ow consumed in the fuel cell. The exhaust temperature acquisition unit acquires the temperature value Tout of the exhaust-side air; and An exhaust humidity estimation unit, which estimates the humidity Hout of the exhaust-side air; The exhaust humidity inference unit calculates the water vapor flow rate WVout in the exhaust-side air based on the formula WF2 - (WF1 - Ow), reads the saturated water vapor quantity corresponding to the temperature value Tout from the memory, obtains the volumetric flow rate of the exhaust-side air using PV=nRT, and uses the formula exhaust-side air humidity% = water vapor flow rate in the exhaust-side air (g / sec) / volumetric flow rate of the exhaust-side air (m). 3 / sec / saturated water vapor content g / m 3 The humidity Hout of the exhaust-side air is inferred by multiplying by 100.

2. The fuel cell system according to claim 1, characterized in that, The fuel cell system also includes a battery temperature acquisition unit for acquiring the temperature of the fuel cell. The exhaust humidity inference unit determines the flow rate of water vapor contained in the intake air based on the temperature obtained by the battery temperature acquisition unit.

3. The fuel cell system according to claim 1 or 2, characterized in that, The fuel cell system also includes an intake-side humidity measurement unit, which measures the amount of water vapor in the intake-side air. The exhaust humidity inference unit subtracts the flow rate of water vapor contained in the intake air from the mass flow rate value WF1 based on the amount of water vapor measured by the intake side humidity measuring unit.

4. The fuel cell system according to claim 1 or 2, characterized in that, The fuel cell system includes: a first mass flow sensor disposed on the inlet side of the fuel cell to measure the mass flow value WF1; and a second mass flow sensor disposed on the exhaust side of the fuel cell to measure the mass flow value WF2.

5. A method for inferring exhaust humidity, characterized in that, This is a method for inferring the exhaust humidity of a fuel cell system, specifically for inferring the humidity of the exhaust air on the fuel cell side. The exhaust humidity inference method includes: The mass flow rate acquisition process involves acquiring the mass flow rate value WF1 of the air intake side of the fuel cell and the mass flow rate value WF2 of the air exhaust side of the fuel cell, respectively. The process of obtaining the mass flow rate value of consumed oxygen is to obtain the mass flow rate value Ow of consumed oxygen in the fuel cell. The exhaust temperature acquisition process acquires the temperature value Tout of the exhaust-side air; and The exhaust-side humidity estimation process calculates the water vapor flow rate WVout in the exhaust-side air based on the mass flow rate value WF2 - (the mass flow rate value WF1 - the oxygen consumption mass flow rate value Ow). It reads the saturated water vapor quantity corresponding to the temperature value Tout from the memory, uses PV=nRT to obtain the volumetric flow rate of the exhaust-side air, and utilizes the formula: exhaust-side air humidity% = water vapor flow rate in exhaust-side air (g / sec) / volumetric flow rate of exhaust-side air (m³). 3 / sec / saturated water vapor content g / m 3 The humidity Hout of the exhaust-side air is inferred by multiplying by 100.

6. The exhaust humidity estimation method according to claim 5, characterized in that, The exhaust humidity inference method further includes a battery temperature acquisition step for obtaining the temperature of the fuel cell. The flow rate of water vapor contained in the intake air is determined based on the obtained temperature.

7. The exhaust humidity estimation method according to claim 5 or 6, characterized in that, The exhaust humidity estimation method further includes an intake-side humidity measurement step, which measures the amount of water vapor in the intake-side air. Based on the measured amount of water vapor, the amount of water vapor contained in the intake air is subtracted from the mass flow rate value WF1.

8. The exhaust humidity estimation method according to claim 5 or 6, characterized in that, The mass flow rate values ​​WF1 and WF2 are measured using a first mass flow rate sensor configured on the inlet side of the fuel cell and a second mass flow rate sensor configured on the exhaust side of the fuel cell, respectively.

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