JP2022170069A - fuel cell system - Google Patents

Abstract

To provide a fuel cell system that can accurately estimate the hydrogen concentration.SOLUTION: In a fuel cell system, a control unit stores a first data group indicating the correlation between the time and the temperature of hydrogen of a predetermined concentration when the hydrogen is discharged to the outside by opening an exhaust and drain valve, and a second data group indicating the correlation between the time and the pressure of the hydrogen in advance, and when the exhaust and drain valve is opened, the second data group is referred to from the change in pressure measured by a pressure sensor to determine whether fuel off-gas is being discharged or the water is being drained. When it is determined that the fuel is being exhausted, the hydrogen concentration in the fuel off-gas is estimated by referring to the first data group from the slope of the temperature change measured by a temperature sensor.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to fuel cell systems.

A fuel cell (FC) is composed of one single cell (hereinafter sometimes referred to as a cell) or a fuel cell stack (hereinafter sometimes simply referred to as a stack) in which a plurality of single cells are stacked, and hydrogen It is a power generation device that extracts electrical energy through an electrochemical reaction between a fuel gas such as gas and an oxidant gas such as oxygen. It should be noted that the fuel gas and oxidant gas that are actually supplied to the fuel cell are often mixtures with gases that do not contribute to oxidation/reduction. In particular, the oxidant gas is often air containing oxygen.
In the following, the fuel gas and the oxidant gas may be simply referred to as "reactant gas" or "gas" without particular distinction. Also, both a single cell and a fuel cell stack in which single cells are stacked may be referred to as a fuel cell.
A single cell of this fuel cell usually includes a membrane electrode assembly (MEA).
A membrane electrode assembly has a catalyst layer and a gas diffusion layer (GDL, hereinafter sometimes simply referred to as a diffusion layer) on both sides of a polymer electrolyte membrane (hereinafter also simply referred to as "electrolyte membrane"). It has a structure formed in order. Therefore, the membrane electrode assembly is sometimes called a membrane electrode gas diffusion layer assembly (MEGA).
A single cell has two separators sandwiching both sides of the membrane electrode gas diffusion layer assembly, if necessary. The separator usually has a structure in which grooves are formed as flow paths for the reaction gas on the surface in contact with the gas diffusion layer. This separator has electronic conductivity and also functions as a current collector for the generated electricity.
At the fuel electrode (anode) of the fuel cell, hydrogen (H ₂ ) as fuel gas supplied from the gas flow path and the gas diffusion layer is protonated by the catalytic action of the catalyst layer, passes through the electrolyte membrane, and reaches the oxidant electrode ( cathode). The co-generated electrons do work through an external circuit and travel to the cathode. Oxygen (O ₂ ) as an oxidant gas supplied to the cathode reacts with protons and electrons in the catalyst layer of the cathode to produce water. The produced water gives moderate humidity to the electrolyte membrane, and excess water permeates the gas diffusion layer and is discharged out of the system.

Various studies have been made on fuel cell systems mounted on fuel cell vehicles (hereinafter sometimes referred to as vehicles).
For example, in Patent Document 1, it is possible to reliably and quickly detect fuel gas concentration changes without increasing the size of the system and while suppressing costs, and it is possible to perform purge control accurately according to the situation in the fuel gas circulation path. A fuel cell system capable of performing

Patent Document 2 discloses a control device for a fuel cell system that accurately estimates the impurity gas concentration in the hydrogen circulation system, reduces the purge amount, saves the driving energy of the circulation pump, and improves the fuel efficiency of the fuel cell system. It is

JP 2005-302456 A JP 2007-012532 A

In a fuel cell system having a fuel gas system including a circulation flow path, impurities such as nitrogen and CO accumulate in the flow path through which the hydrogen fuel gas is circulated, and the hydrogen partial pressure gradually drops. continue. Therefore, it is important to manage the hydrogen concentration in the circulation channel.
In addition to Patent Document 1, direct measurement of hydrogen concentration with a hydrogen concentration sensor is also a candidate, but all of them, including the technology of Patent Document 1, are easily affected by water, and there is a concern of erroneous detection. It is also possible to install these sensors in the gas space in the gas-liquid separator, but there is a risk of erroneous detection due to the influence of condensed water.

The present disclosure has been made in view of the above circumstances, and a main object thereof is to provide a fuel cell system capable of accurately estimating the hydrogen concentration.

The fuel cell system of the present disclosure is a fuel cell system,
The fuel cell system includes a fuel cell,
a fuel gas supply unit for supplying a fuel gas containing hydrogen to the fuel cell;
a fuel gas supply channel connecting the fuel gas supply unit and a fuel gas inlet of the fuel cell;
an ejector arranged in the fuel gas supply channel;
a circulation flow path that connects the fuel gas outlet of the fuel cell and the ejector, recovers the fuel off-gas discharged from the fuel gas outlet, and supplies it to the fuel cell as a circulation gas;
a gas-liquid separator disposed in the circulation channel and configured to separate and recover the fuel off-gas and moisture;
a fuel off-gas discharge channel connected to the gas-liquid separator;
an exhaust drain valve disposed in the fuel off-gas discharge channel;
a temperature sensor provided in the exhaust drain valve;
a pressure sensor arranged in at least one channel selected from the group consisting of the fuel gas supply channel and the circulation channel;
a control unit;
The control unit comprises a first data group showing the correlation between the time and the temperature of the hydrogen when the exhaust and drain valve is opened and the hydrogen of a predetermined concentration is exhausted to the outside, and the time and the pressure of the hydrogen. pre-store a second data group showing the correlation of
When the exhaust/drain valve is opened, the control unit refers to the second data group to determine whether the fuel off-gas is being discharged or the water is being drained, based on the pressure change measured by the pressure sensor. judge,
The control unit estimates the concentration of hydrogen in the fuel off-gas by referring to the first data group from the slope of the temperature change measured by the temperature sensor when it is determined that the gas is being exhausted. do.

In the fuel cell system of the present disclosure, when the control unit determines that the exhaust is in progress, the slope of the temperature change measured by the temperature sensor refers to the first data group to obtain a predetermined temperature change slope. Determine whether it is smaller than the threshold,
The control unit may detect that the hydrogen concentration is abnormal when determining that the slope of the temperature change measured by the temperature sensor is smaller than the predetermined temperature change slope threshold.

In the fuel cell system of the present disclosure, when the controller determines that the slope of the temperature change measured by the temperature sensor is smaller than the predetermined temperature change slope threshold value, the pressure measured by the pressure sensor is smaller than a predetermined pressure change slope threshold with reference to the second data group,
The control unit detects clogging of the exhaust/drain valve when determining that the slope of the pressure change measured by the pressure sensor is smaller than the predetermined pressure change slope threshold, and
The control unit may detect that the hydrogen concentration is abnormal when determining that the slope of the pressure change measured by the pressure sensor is equal to or greater than the predetermined pressure change slope threshold.

According to the fuel cell system of the present disclosure, it is possible to accurately estimate the hydrogen concentration.

FIG. 1 is a diagram showing an example of the relationship between time and temperature in the case of normal hydrogen concentration and in the case of abnormal hydrogen concentration. FIG. 2 is a diagram showing an example of the relationship between time and pressure in the case of normal hydrogen concentration and in the case of abnormal hydrogen concentration. FIG. 3 is a schematic configuration diagram showing an example of the fuel cell system of the present disclosure. FIG. 4 is a flow chart showing an example of control of the fuel cell system of the present disclosure.

The fuel cell system of the present disclosure is a fuel cell system,
The fuel cell system includes a fuel cell,
a fuel gas supply unit for supplying a fuel gas containing hydrogen to the fuel cell;
a fuel gas supply channel connecting the fuel gas supply unit and a fuel gas inlet of the fuel cell;
an ejector arranged in the fuel gas supply channel;
a circulation flow path that connects the fuel gas outlet of the fuel cell and the ejector, recovers the fuel off-gas discharged from the fuel gas outlet, and supplies it to the fuel cell as a circulation gas;
a gas-liquid separator disposed in the circulation channel and configured to separate and recover the fuel off-gas and moisture;
a fuel off-gas discharge channel connected to the gas-liquid separator;
an exhaust drain valve disposed in the fuel off-gas discharge channel;
a temperature sensor provided in the exhaust drain valve;
a pressure sensor arranged in at least one channel selected from the group consisting of the fuel gas supply channel and the circulation channel;
a control unit;
The control unit comprises a first data group showing the correlation between the time and the temperature of the hydrogen when the exhaust and drain valve is opened and the hydrogen of a predetermined concentration is exhausted to the outside, and the time and the pressure of the hydrogen. pre-store a second data group showing the correlation of
When the exhaust/drain valve is opened, the control unit refers to the second data group to determine whether the fuel off-gas is being discharged or the water is being drained, based on the pressure change measured by the pressure sensor. judge,
The control unit estimates the concentration of hydrogen in the fuel off-gas by referring to the first data group from the slope of the temperature change measured by the temperature sensor when it is determined that the gas is being exhausted. do.

There is a need to detect hydrogen concentration abnormalities and ejector failures in the fuel gas system including the circulation flow path. Ultimately, it is possible to detect abnormalities in hydrogen concentration by monitoring the voltage value of the voltage sensor when the hydrogen concentration becomes insufficient and the voltage of the fuel cell drops. If not, the abnormality cannot be detected.
As an existing technology for detecting abnormalities in hydrogen concentration, there is a method of directly measuring hydrogen concentration by placing a hydrogen concentration sensor in the fuel gas system, but in this case, the hydrogen concentration sensor is easily affected by water and makes false detections. , the mountability deteriorates, and the cost increases.
In addition, there is an existing technology that places a hydrogen concentration sensor in the gas-liquid separator, but since the gas-liquid separation rate is not 100%, it is not possible to avoid 100% water, and there is a possibility of false detection due to condensation water. , it is not possible to completely prevent false detections due to water.

In the present disclosure, since the hydrogen concentration sensor that can accurately detect or estimate the hydrogen concentration is vulnerable to water, hydrogen concentration estimation and hydrogen concentration abnormality are detected at a part where the timing with water/no water is clear. do. Specifically, a temperature sensor is installed in the exhaust drain valve, and when the exhaust drain valve is opened, the pressure value of the fuel system gas flowing through the fuel gas flow path determines whether it is being drained or exhausted. Hydrogen concentration is estimated and abnormal hydrogen concentration is detected from the temperature change of the exhaust drain valve.
According to the present disclosure, since the hydrogen concentration in the circulation channel can be estimated with high accuracy, an abnormality (ejector failure, etc.) in the circulation channel can be detected.

Hydrogen has a thermal conductivity of 0.214 (W/m K @ 100°C), nitrogen has a thermal conductivity of 0.0313 (W/m K @ 100°C), and water vapor has a thermal conductivity of 0.0241 ( W/m·K @ 100° C.), hydrogen has a higher thermal conductivity than other gases (nitrogen, water vapor), and the speed of heat transfer increases. Also, there are estimated values for normal hydrogen concentration and other gases. Using these, it is possible to estimate the temperature change of the exhaust drain valve during normal operation during exhaust. Abnormalities in the hydrogen concentration are detected by comparing the change in temperature of the exhaust drain valve during normal operation during exhaust with the change in temperature of the exhaust drain valve measured by the temperature sensor.
FIG. 1 is a diagram showing an example of the relationship between time and temperature when the hydrogen concentration is normal and when the hydrogen concentration is abnormal.
As shown in FIG. 1, the temperature does not change during drainage. In addition, since the temperature change rate differs between the hydrogen concentration in the normal state and the hydrogen concentration in the abnormal state, the temperature change rate for the hydrogen concentration in the normal state is stored in advance, and the measured value is used. By comparing the hydrogen concentration, it is possible to estimate the hydrogen concentration with high accuracy, and unlike the temperature change rate when the measured value is the normal hydrogen concentration, when the temperature change in the exhaust gas is small, the hydrogen concentration abnormality can be detected. can.

Abnormal hydrogen concentration also occurs when the exhaust drain valve is clogged, but in the case of clogging, not only abnormal temperature changes but also abnormal pressure changes occur at the same time, so it is possible to distinguish from the pressure behavior during exhaust. be.
FIG. 2 is a diagram showing an example of the relationship between time and pressure in the case of normal hydrogen concentration and in the case of abnormal hydrogen concentration.
As shown in Figure 2, the pressure does not change during draining. In addition, since the pressure change rate differs between the normal hydrogen concentration in the exhaust and the abnormal hydrogen concentration, the pressure change rate for the normal hydrogen concentration is stored in advance, and the measured value is measured. are compared, and when the temperature change during exhaust is small and the pressure drop is small, it can be determined that the exhaust drain valve is clogged (half-open abnormality).

In the present disclosure, fuel gas and oxidant gas are collectively referred to as reaction gas. The reactant gas supplied to the anode is fuel gas, and the reactant gas supplied to the cathode is oxidant gas. The fuel gas is a gas containing primarily hydrogen and may be hydrogen. The oxidant gas may be oxygen, air, dry air, or the like.

The fuel cell system of the present disclosure is usually used by being mounted on a vehicle having an electric motor as a drive source.
Also, the fuel cell system of the present disclosure may be used by being mounted on a vehicle that can run on the power of a secondary battery.
The vehicle may be a fuel cell vehicle.
A vehicle may include the fuel cell system of the present disclosure.
The electric motor is not particularly limited, and may be a conventionally known drive motor.

A fuel cell system of the present disclosure includes a fuel cell.
The fuel cell may have only one unit cell, or may be a fuel cell stack, which is a stack of a plurality of unit cells.
The number of stacked single cells is not particularly limited, and may be, for example, 2 to several hundred, or 2 to 600.
The fuel cell stack may have end plates at both ends in the stacking direction of the unit cells.

A single cell of a fuel cell comprises at least a membrane electrode gas diffusion layer assembly.
The membrane electrode gas diffusion layer assembly has an anode-side gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode-side gas diffusion layer in this order.

The cathode (oxidant electrode) includes a cathode catalyst layer and a cathode-side gas diffusion layer.
The anode (fuel electrode) includes an anode catalyst layer and an anode-side gas diffusion layer.
The cathode catalyst layer and the anode catalyst layer are collectively referred to as catalyst layers. Examples of the anode catalyst and the cathode catalyst include Pt (platinum) and Ru (ruthenium). Examples of the base material and conductive material that support the catalyst include carbon materials such as carbon.

The cathode-side gas diffusion layer and the anode-side gas diffusion layer are collectively referred to as gas diffusion layers.
The gas diffusion layer may be a conductive member or the like having gas permeability.
Examples of the conductive member include porous carbon bodies such as carbon cloth and carbon paper, and porous metal bodies such as metal mesh and metal foam.

The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of solid polymer electrolyte membranes include fluorine-based electrolyte membranes such as perfluorosulfonic acid thin films containing moisture, and hydrocarbon-based electrolyte membranes. As the electrolyte membrane, for example, a Nafion membrane (manufactured by DuPont) may be used.

A single cell may be provided with two separators sandwiching both sides of the membrane electrode gas diffusion layer assembly, if necessary. One of the two separators is an anode separator and the other is a cathode separator. In the present disclosure, the anode side separator and the cathode side separator are collectively referred to as separators.
The separator may have a supply hole and a discharge hole for circulating fluids such as reaction gas and coolant in the stacking direction of the unit cells. As the coolant, for example, a mixed solution of ethylene glycol and water can be used to prevent freezing at low temperatures.
The supply holes include a fuel gas supply hole, an oxidant gas supply hole, a coolant supply hole, and the like.
Examples of the discharge holes include a fuel gas discharge hole, an oxidant gas discharge hole, a refrigerant discharge hole, and the like.
The separator may have one or more fuel gas supply holes, one or more oxidant gas supply holes, and one or more refrigerant supply holes. , may have one or more fuel gas discharge holes, may have one or more oxidant gas discharge holes, and may have one or more refrigerant discharge holes.
The separator may have reaction gas channels on the surface in contact with the gas diffusion layer. Moreover, the separator may have a coolant channel for keeping the temperature of the fuel cell constant on the surface opposite to the surface in contact with the gas diffusion layer.
When the separator is the anode-side separator, it may have one or more fuel gas supply holes, one or more oxidant gas supply holes, and one or more coolant supply holes. , may have one or more fuel gas discharge holes, may have one or more oxidant gas discharge holes, and may have one or more refrigerant discharge holes The anode-side separator may have a fuel gas channel for flowing fuel gas from the fuel gas supply hole to the fuel gas discharge hole on the surface in contact with the anode-side gas diffusion layer. The surface opposite to the surface in contact with the layer may have a coolant channel through which the coolant flows from the coolant supply hole to the coolant discharge hole.
When the separator is a cathode-side separator, it may have one or more fuel gas supply holes, one or more oxidant gas supply holes, and one or more coolant supply holes. , may have one or more fuel gas discharge holes, may have one or more oxidant gas discharge holes, and may have one or more refrigerant discharge holes The cathode-side separator may have an oxidizing gas channel for flowing the oxidizing gas from the oxidizing gas supply hole to the oxidizing gas discharge hole on the surface in contact with the cathode-side gas diffusion layer, The surface opposite to the surface in contact with the cathode-side gas diffusion layer may have a coolant channel for flowing the coolant from the coolant supply hole to the coolant discharge hole.
The separator may be a gas-impermeable conductive member or the like. The conductive member may be, for example, dense carbon that is gas-impermeable by compressing carbon, or a press-molded metal (eg, iron, aluminum, stainless steel, etc.) plate. Also, the separator may have a current collecting function.

The fuel cell stack may have manifolds such as an inlet manifold with which each supply hole communicates and an outlet manifold with which each discharge hole communicates.
The inlet manifold includes an anode inlet manifold, a cathode inlet manifold, a coolant inlet manifold, and the like.
The outlet manifold includes an anode outlet manifold, a cathode outlet manifold, a coolant outlet manifold, and the like.

The fuel cell system includes, as a fuel gas system of the fuel cell, a fuel gas supply unit, a fuel gas supply channel, an ejector, a circulation channel, a gas-liquid separator, a fuel off-gas discharge channel, and an exhaust/drain valve. , a temperature sensor, a pressure sensor, and a controller.

The fuel gas supply unit supplies fuel gas containing hydrogen to the fuel cell. Specifically, the fuel gas supply unit supplies fuel gas containing hydrogen to the anode of the fuel cell.
Examples of the fuel gas supply unit include fuel tanks, and more specifically, liquid hydrogen tanks, compressed hydrogen tanks, and the like.
The fuel gas supply section is electrically connected to the control section. The fuel gas supply unit may control ON/OFF of supply of the fuel gas to the fuel cell by controlling opening/closing of a main stop valve of the fuel gas supply unit according to the control signal from the control unit.

The fuel gas supply channel connects the fuel gas supply section and the fuel gas inlet of the fuel cell. The fuel gas supply channel enables the supply of fuel gas to the anode of the fuel cell. The fuel gas inlet may be a fuel gas feed hole, an anode inlet manifold, or the like.

An ejector is arranged in the fuel gas supply channel.
The ejector may be arranged, for example, at the confluence of the fuel gas supply channel and the circulation channel. The ejector supplies a mixed gas containing fuel gas and circulation gas to the anode of the fuel cell. A conventionally known ejector can be employed as the ejector.

A pressure regulating valve and a medium-pressure hydrogen sensor may be arranged in a region of the fuel gas supply channel between the fuel gas supply portion and the ejector.
The pressure regulating valve regulates the pressure of fuel gas supplied from the fuel gas supply section to the ejector.
The pressure regulating valve may be electrically connected to the control unit, and the pressure of the fuel gas supplied to the ejector may be adjusted by controlling the opening/closing and the degree of opening of the pressure regulating valve by the control unit.
The medium-pressure hydrogen sensor is electrically connected to the control unit, and the control unit detects the pressure of the fuel gas measured by the medium-pressure hydrogen sensor, and controls the opening/closing and the degree of opening of the pressure regulating valve based on the detected pressure. Thereby, the pressure of the fuel gas supplied to the ejector may be adjusted.

The circulation channel connects the fuel gas outlet of the fuel cell and the ejector.
The circulation flow path makes it possible to collect the fuel off-gas, which is the fuel gas discharged from the fuel gas outlet of the fuel cell, and supply it to the fuel cell as circulation gas.
The circulation flow path may join the fuel gas supply flow path by connecting with an ejector arranged in the fuel gas supply flow path.

A circulation pump may be arranged in the circulation channel. The circulation pump circulates the fuel off-gas as circulation gas. The circulating pump may be electrically connected to the control unit, and the flow rate of the circulating gas may be adjusted by controlling on/off of the driving of the circulating pump, the number of revolutions, etc. of the circulating pump by the control unit.

A gas-liquid separator (anode gas-liquid separator) may be arranged in the circulation channel.
The gas-liquid separator may be arranged at a branch point between the fuel off-gas discharge channel and the circulation channel.
The circulation flow path branches from the fuel off-gas discharge flow path, and may join the fuel gas supply flow path by connecting to an ejector arranged in the fuel gas supply flow path.
The circulation flow path may be branched from the fuel off-gas discharge flow path via a gas-liquid separator, and may join the fuel gas supply flow path by connecting to an ejector arranged in the fuel gas supply flow path.
The gas-liquid separator is arranged upstream of the exhaust drain valve in the fuel off-gas discharge channel.
The gas-liquid separator separates fuel off-gas, which is the fuel gas discharged from the fuel gas outlet, and moisture (liquid water). As a result, the fuel off-gas may be returned to the circulation flow path as a circulation gas, or unnecessary gas, moisture, etc. may be discharged to the outside by opening the exhaust/drain valve of the fuel off-gas discharge flow path. In addition, since the gas-liquid separator can prevent excess water from flowing into the circulation flow path, it is possible to prevent the circulation pump from freezing due to the water.

The fuel off-gas discharge channel is connected to the gas-liquid separator.
The fuel off-gas discharge channel may connect the fuel gas outlet of the fuel cell and the outside of the fuel cell system, and a gas-liquid separator may be arranged in the region between the fuel gas outlet and the outside of the fuel cell system. .
The fuel off-gas discharge channel may branch from the circulation channel via a gas-liquid separator.
The fuel off-gas discharge channel discharges the fuel off-gas discharged from the fuel gas outlet of the fuel cell to the outside of the fuel cell system. The fuel gas outlet may be a fuel gas outlet, an anode outlet manifold, or the like.

An exhaust drain valve (fuel off-gas discharge valve) is arranged in the fuel off-gas discharge flow path. The exhaust drain valve is arranged downstream of the gas-liquid separator.
The exhaust/drain valve allows fuel off-gas, moisture, and the like to be discharged to the outside (outside the system). The outside may be the outside of the fuel cell system or the outside of the vehicle.
The exhaust drain valve is electrically connected to the control unit, and the control unit controls the opening and closing of the exhaust drain valve to adjust the flow rate of fuel off-gas discharged to the outside and the drain flow rate of water (liquid water). good too. Also, the pressure of the fuel gas supplied to the anode of the fuel cell (anode pressure) may be adjusted by adjusting the opening degree of the exhaust/drain valve.
The fuel off-gas may include the fuel gas that has passed through the anode without reaction, water that has reached the anode from the water produced at the cathode, and the like. The fuel off-gas may contain corrosive substances generated in the catalyst layer, the electrolyte membrane, and the like, and oxidant gas that may be supplied to the anode during scavenging.

A temperature sensor is provided on the exhaust drain valve.
A temperature sensor measures the temperature of the fuel off-gas passing through the exhaust drain valve.
The temperature sensor is electrically connected to the controller, and the controller detects the temperature of the fuel off-gas measured by the temperature sensor.
A conventionally known thermometer or the like can be used as the temperature sensor.

The pressure sensor may be arranged in at least one channel selected from the group consisting of the fuel gas supply channel and the circulation channel, and may be arranged in both channels.
The pressure sensor measures the pressure of the fuel system gas passing through at least one channel selected from the group consisting of the fuel gas supply channel and the circulation channel. The fuel system gas is at least one kind of gas selected from the group consisting of fuel gas, fuel off-gas, and circulating gas.
The pressure sensor is electrically connected to the controller, and the controller detects the pressure of the fuel system gas measured by the pressure sensor.
A conventionally known pressure gauge or the like can be used as the pressure sensor.

The fuel cell system may include an oxidant gas supply unit, an oxidant gas supply channel, or an oxidant off-gas discharge channel as an oxidant gas system of the fuel cell. Alternatively, an oxidant gas bypass flow path may be provided, a bypass valve may be provided, and an oxidant gas flow rate sensor may be provided.
The oxidant gas supply unit supplies oxidant gas to the fuel cell. Specifically, the oxidant gas supply section supplies the oxidant gas to the cathode of the fuel cell.
For example, an air compressor or the like can be used as the oxidant gas supply unit.
The oxidant gas supply section is electrically connected to the control section. The oxidant gas supply section is driven according to a control signal from the control section. The oxidizing gas supply unit may have at least one selected from the group consisting of flow rate and pressure of the oxidizing gas supplied from the oxidizing gas supply unit to the cathode by the control unit.
The oxidant gas supply channel connects the oxidant gas supply unit and the oxidant gas inlet of the fuel cell. The oxidant gas supply channel enables the supply of oxidant gas from the oxidant gas supply to the cathode of the fuel cell. The oxidant gas inlet may be an oxidant gas supply hole, a cathode inlet manifold, or the like.
The oxidant off-gas discharge channel is connected to the oxidant gas outlet of the fuel cell. The oxidant off-gas discharge channel enables the oxidant off-gas, which is the oxidant gas discharged from the cathode of the fuel cell, to be discharged to the outside. The oxidant gas outlet may be an oxidant gas outlet, a cathode outlet manifold, or the like.
An oxidant gas pressure control valve may be provided in the oxidant off-gas discharge channel.
The oxidizing gas pressure regulating valve is electrically connected to the control unit, and the oxidizing gas pressure regulating valve is opened by the control unit to discharge the oxidizing off gas, which is the oxidizing gas that has already reacted. It is discharged to the outside from the channel. Also, the pressure of the oxidizing gas supplied to the cathode (cathode pressure) may be adjusted by adjusting the opening degree of the oxidizing gas pressure regulating valve.
The oxidant gas bypass channel branches from the oxidant gas supply channel, bypasses the fuel cell, and connects the branch portion of the oxidant gas supply channel and the confluence portion of the oxidant offgas discharge channel.
A bypass valve is arranged in the oxidant gas bypass channel.
The bypass valve is electrically connected to the control unit, and is opened by the control unit to bypass the fuel cell and supply the oxidant gas when the supply of the oxidant gas to the fuel cell is unnecessary. It can be discharged to the outside from the oxidant off-gas discharge channel.
The oxidizing gas flow rate sensor is arranged in the oxidizing gas supply channel.
The oxidant gas flow rate sensor detects the flow rate of the oxidant gas in the oxidant gas system. The oxidant gas flow rate sensor is electrically connected to the controller. The control unit may estimate the rotation speed of the air compressor from the flow rate of the oxidizing gas detected by the oxidizing gas flow rate sensor. The oxidizing gas flow rate sensor may be arranged upstream of the oxidizing gas supply section of the oxidizing gas supply channel.
A conventionally known flow meter or the like can be adopted as the oxidant gas flow rate sensor.

The fuel cell system may include a coolant supply section as a cooling system for the fuel cell, and may include a coolant circulation channel.
The coolant circulation channel communicates with the coolant supply hole and the coolant discharge hole provided in the fuel cell, and allows the coolant supplied from the coolant supply section to circulate inside and outside the fuel cell.
The coolant supply section is electrically connected to the control section. The coolant supply section is driven according to a control signal from the control section. The coolant supply unit has the flow rate of the coolant supplied from the coolant supply unit to the fuel cell controlled by the control unit. This may control the temperature of the fuel cell.
The coolant supply unit may be, for example, a cooling water pump.
A radiator that radiates heat from the cooling water may be provided in the coolant circulation flow path.
A reserve tank for storing the coolant may be provided in the coolant circulation channel.

The fuel cell system may include a secondary battery.
The secondary battery (battery) may be any chargeable/dischargeable battery, and examples thereof include conventionally known secondary batteries such as nickel-metal hydride secondary batteries and lithium-ion secondary batteries. Also, the secondary battery may include an electric storage element such as an electric double layer capacitor. A plurality of secondary batteries may be connected in series. The secondary battery supplies electric power to the electric motor, the oxidant gas supply unit, and the like. The secondary battery may be, for example, rechargeable from a power source outside the vehicle such as a household power source. The secondary battery may be charged by the output of the fuel cell. Charging and discharging of the secondary battery may be controlled by the controller.

The control unit physically includes, for example, an arithmetic processing unit such as a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores control programs and control data processed by the CPU, and a main control unit. It has a storage device such as a RAM (random access memory) used as various work areas for processing, and an input/output interface. Also, the control unit may be a control device such as an electronic control unit (ECU).
The control unit may be electrically connected to an ignition switch that may be mounted on the vehicle. The control unit may be operable by an external power source even when the ignition switch is turned off.

The control unit opens the exhaust/drain valve and exhausts hydrogen of a predetermined concentration to the outside. Two data groups are stored in advance.
The predetermined concentration may be the concentration of hydrogen normally contained in the fuel gas, and the concentration within the allowable range and outside the allowable range for normal operation of the fuel cell for determining hydrogen concentration abnormality. may be
The first data group may be, for example, a data group as shown in FIG.
The second data group may be, for example, a data group as shown in FIG.

When the exhaust/drain valve is opened, the control unit refers to the second data group to determine whether fuel off-gas is being discharged or water is being drained, based on the change in pressure measured by the pressure sensor.
As shown in FIG. 2, there is no pressure change when the water is being drained, and a pressure change occurs when the water is being discharged.

The controller estimates the concentration of hydrogen in the fuel off-gas by referring to the first data group from the slope of the temperature change measured by the temperature sensor when it is determined that the exhaust is being performed.
When determining that the air is being exhausted, the control unit may refer to the first data group to determine whether or not the slope of the temperature change measured by the temperature sensor is smaller than a predetermined temperature change slope threshold.
The controller may detect that the hydrogen concentration is abnormal when it determines that the slope of the temperature change measured by the temperature sensor is smaller than a predetermined temperature change slope threshold. On the other hand, the control unit may detect that the hydrogen concentration is normal when determining that the slope of temperature change measured by the temperature sensor is equal to or greater than a predetermined temperature change slope threshold.
The temperature change gradient threshold may be appropriately set as a temperature change gradient that serves as a reference for determining whether the hydrogen concentration is within a normal range that does not interfere with the operation of the fuel cell. The temperature change slope threshold value may be a temperature change slope when the fuel cell generates power using a normal fuel gas containing a predetermined concentration of hydrogen stored in advance.

When the controller determines that the slope of the temperature change measured by the temperature sensor is smaller than a predetermined temperature change slope threshold, the controller refers to the second data group for the slope of the pressure change measured by the pressure sensor. It may be determined whether or not the pressure change gradient threshold value is smaller than a predetermined pressure change slope threshold.
The control unit may detect clogging of the exhaust/drain valve when determining that the slope of the pressure change measured by the pressure sensor is smaller than a predetermined pressure change slope threshold value.
On the other hand, the control unit may detect that the hydrogen concentration is abnormal when it determines that the slope of the pressure change measured by the pressure sensor is equal to or greater than a predetermined pressure change slope threshold.
The pressure change slope threshold may be appropriately set as a pressure change slope that serves as a reference for determining whether the fuel gas pressure is within a normal range that does not interfere with the operation of the fuel cell. The pressure change slope threshold value may be the pressure change slope when the fuel cell generates power using a normal fuel gas containing hydrogen at a prescribed concentration stored in advance.
As shown in FIG. 2, when the exhaust/drain valve is clogged, the slope of the pressure change becomes smaller, so the clogging of the exhaust/drain valve can be detected by comparing the normal pressure slope with the measured value.

FIG. 3 is a schematic configuration diagram showing an example of the fuel cell system of the present disclosure.
A fuel cell system 100 shown in FIG. , a circulation channel 25 , an ejector 26 , a controller 50 , a temperature sensor 60 and a pressure sensor 70 . Note that FIG. 3 shows only the fuel gas system, and omits the illustration of the oxidant gas system, the cooling system, and the like.

FIG. 4 is a flow chart showing an example of control of the fuel cell system of the present disclosure.
First, the controller detects the pressure measured by the pressure sensor when the exhaust/drain valve is opened.
Then, based on the presence or absence of pressure change, the control unit refers to the second data group and determines whether fuel off-gas is being discharged or water is being drained.
Then, when it is determined that there is a pressure change and that the exhaust is being performed, the control unit refers to the first data group and estimates the hydrogen concentration in the fuel off-gas from the slope of the temperature change measured by the temperature sensor.
When determining that the air is being exhausted, the control unit refers to the first data group and determines whether or not the slope of the temperature change measured by the temperature sensor is smaller than a predetermined temperature change slope threshold.
When the controller determines that the slope of the temperature change measured by the temperature sensor is equal to or greater than a predetermined temperature change slope threshold value, the control unit detects that the hydrogen concentration is normal and ends the control.
On the other hand, when the control unit determines that the slope of the temperature change measured by the temperature sensor is smaller than the predetermined temperature change slope threshold value, the slope of the pressure change measured by the pressure sensor does not correspond to the second data group. By referring to it, it is determined whether or not it is smaller than a predetermined pressure change slope threshold.
When the control unit determines that the slope of the pressure change measured by the pressure sensor is smaller than a predetermined pressure change slope threshold value, it detects that the exhaust/drain valve is clogged and ends the control.
On the other hand, when the control unit determines that the slope of the pressure change measured by the pressure sensor is equal to or greater than the predetermined pressure change slope threshold value, it detects that the hydrogen concentration is abnormal and ends the control.

10 Fuel cell 20 Fuel gas supply unit 21 Fuel gas supply channel 22 Fuel off-gas discharge channel 23 Exhaust drain valve 24 Gas-liquid separator 25 Circulation channel 26 Ejector 50 Control unit 60 Temperature sensor 70 Pressure sensor 100 Fuel cell system

Claims (3)

A fuel cell system,
The fuel cell system includes a fuel cell,
a fuel gas supply unit for supplying a fuel gas containing hydrogen to the fuel cell;
a fuel gas supply channel connecting the fuel gas supply unit and a fuel gas inlet of the fuel cell;
an ejector arranged in the fuel gas supply channel;
a circulation flow path that connects the fuel gas outlet of the fuel cell and the ejector, recovers the fuel off-gas discharged from the fuel gas outlet, and supplies it to the fuel cell as a circulation gas;
a gas-liquid separator disposed in the circulation channel and configured to separate and recover the fuel off-gas and moisture;
a fuel off-gas discharge channel connected to the gas-liquid separator;
an exhaust drain valve disposed in the fuel off-gas discharge channel;
a temperature sensor provided in the exhaust drain valve;
a pressure sensor arranged in at least one channel selected from the group consisting of the fuel gas supply channel and the circulation channel;
a control unit;
The control unit comprises a first data group showing the correlation between the time and the temperature of the hydrogen when the exhaust and drain valve is opened and the hydrogen of a predetermined concentration is exhausted to the outside, and the time and the pressure of the hydrogen. pre-store a second data group showing the correlation of
When the exhaust/drain valve is opened, the control unit refers to the second data group to determine whether the fuel off-gas is being discharged or the water is being drained, based on the pressure change measured by the pressure sensor. judge,
The control unit estimates the concentration of hydrogen in the fuel off-gas by referring to the first data group from the slope of the temperature change measured by the temperature sensor when it is determined that the gas is being exhausted. fuel cell system. When determining that the exhaust is being performed, the control unit refers to the first data group to determine whether or not the slope of the temperature change measured by the temperature sensor is smaller than a predetermined temperature change slope threshold. ,
2. The fuel according to claim 1, wherein the controller detects that the hydrogen concentration is abnormal when it determines that the slope of the temperature change measured by the temperature sensor is smaller than the predetermined temperature change slope threshold. battery system. When the controller determines that the slope of the change in temperature measured by the temperature sensor is smaller than the predetermined slope threshold for temperature change, the controller determines that the slope of the change in pressure measured by the pressure sensor exceeds the second slope. referring to the data group to determine whether it is smaller than a predetermined pressure change slope threshold;
The control unit detects clogging of the exhaust/drain valve when determining that the slope of the pressure change measured by the pressure sensor is smaller than the predetermined pressure change slope threshold, and
3. The fuel according to claim 2, wherein the controller detects that the hydrogen concentration is abnormal when it determines that the pressure change slope measured by the pressure sensor is greater than or equal to the predetermined pressure change slope threshold value. battery system.

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