JP2021086756A - Fuel cell system - Google Patents

Abstract

To provide a fuel cell system capable of generating power with stability.SOLUTION: A fuel cell system comprises: a fuel cell stack 31 that generates power through chemical reaction between a fuel gas and an oxidant gas; and a fuel gas supply device 60 that supplies the fuel gas to the fuel cell stack. The fuel cell system further comprises: an oxidant gas supply device 50 that supplies the oxidant gas to the fuel cell stack, and cools the fuel cell stack; and a control part 90 for controlling the power generation by the fuel cell stack. The fuel cell stack includes a fuel inlet part 32 and a fuel outlet part 33. The fuel cell stack further includes: a fuel upstream part 31u that is a part, which is closer to the fuel inlet part than the fuel outlet part, of the fuel cell stack; and a fuel downstream part 31d that is a part, which is closer to the fuel outlet part than the fuel inlet part, of the fuel cell stack. The control part controls the oxidant gas supply device so that a temperature of the fuel downstream part becomes higher than a temperature of the fuel upstream part.SELECTED DRAWING: Figure 1

Description

The disclosure herein relates to a fuel cell system.

Patent Document 1 discloses a separator plate for an air-cooled fuel cell. The contents of the prior art document are incorporated by reference as an explanation of the technical elements in this specification.

Special Table 2017-510954

In a fuel cell, water vapor generated on the cathode side may move to the anode side due to backdiffusion. When the water vapor that has moved to the anode side is cooled and condensed, it becomes liquid water, which hinders the smooth flow of fuel gas on the anode side. A fuel cell is in a state where it cannot generate an appropriate amount of power unless a fuel gas is appropriately supplied.

The movement of water vapor to the anode side due to backdiffusion or the like can occur regardless of the location from the upstream to the downstream of the fuel gas flow. Therefore, the portion located downstream in the flow of the fuel gas is likely to contain a large amount of water vapor and is likely to condense to generate liquid water. Further improvements are required in the fuel cell system in the above-mentioned viewpoint or in other viewpoints not mentioned.

One object disclosed is to provide a fuel cell system capable of stable power generation.

The fuel cell system disclosed herein includes a fuel cell stack (31) that generates power by a chemical reaction between a fuel gas and an oxidizing agent gas, and a fuel gas supply device (60) for supplying fuel gas to the fuel cell stack. , Equipped with an oxidant gas supply device (50, 250, 350) for supplying the oxidant gas to the fuel cell stack and cooling the fuel cell stack, and a control unit (90) for controlling the power generation of the fuel cell stack. The fuel cell stack includes a fuel inlet portion (32) for introducing the fuel gas into the fuel cell stack, a fuel outlet portion (33) for deriving the fuel gas from the inside of the fuel cell stack, and a fuel cell stack. The fuel upstream portion (31u), which is closer to the fuel inlet portion than the fuel outlet portion, and the fuel downstream portion (31d), which is a portion of the fuel cell stack closer to the fuel outlet portion than the fuel inlet portion, are provided. The control unit controls the oxidant gas supply device so that the temperature of the downstream portion of the fuel becomes higher than the temperature of the upstream portion of the fuel.

According to the disclosed fuel cell system, a control unit for controlling the oxidant gas supply device so that the temperature of the downstream portion of the fuel becomes higher than the temperature of the upstream portion of the fuel is provided. Therefore, it is easy to prevent the water vapor from being cooled and condensed in the downstream portion of the fuel, which tends to contain a large amount of water vapor in the fuel gas. Therefore, the smooth flow of fuel gas is not easily obstructed by the condensed water, and it is easy to maintain an appropriate fuel gas supply. Therefore, it is possible to provide a fuel cell system capable of generating electricity in a stable manner.

The disclosed aspects herein employ different technical means to achieve their respective objectives. The claims and the reference numerals in parentheses described in this section exemplify the correspondence with the parts of the embodiments described later, and are not intended to limit the technical scope. The objectives, features, and effects disclosed herein will be made clearer by reference to the subsequent detailed description and accompanying drawings.

It is a block diagram which shows the fuel cell system. It is explanatory drawing for demonstrating supply of reaction gas to a fuel cell stack. It is an exploded perspective view which shows the fuel cell. It is an enlarged perspective view which shows the fuel cell. It is sectional drawing which shows the flow of the fuel gas in the fuel cell stack. It is a block diagram concerning the control of a fuel cell system. It is a flowchart about control of a fuel cell system. It is a block diagram which shows the fuel cell system in 2nd Embodiment. It is a block diagram which shows the fuel cell system in 3rd Embodiment.

A plurality of embodiments will be described with reference to the drawings. In a plurality of embodiments, functionally and / or structurally corresponding parts and / or related parts may be designated with the same reference code or reference codes having a hundreds or more different digits. References can be made to the description of other embodiments for the corresponding and / or associated parts. In the following, the three directions orthogonal to each other will be referred to as the X direction, the Y direction, and the Z direction.

The first embodiment is a system that generates electricity by a chemical reaction between a fuel gas and an oxidant gas. The fuel cell system 1 is mounted on, for example, a fuel cell hybrid vehicle (FCHV) and generates electric power to be supplied to a traveling motor. Further, the fuel cell system 1 is a stationary fuel cell system that simultaneously extracts electricity and heat to supply hot water and heat.

In FIG. 1, the fuel cell system 1 includes a fuel cell stack 31, an oxidant gas supply device 50, and a fuel gas supply device 60. The fuel cell stack 31 is a power generation device that generates power by a chemical reaction between an oxidant gas and a fuel gas. The fuel cell stack 31 includes a fuel inlet portion 32 for introducing fuel gas into the fuel cell stack 31. The fuel cell stack 31 includes a fuel outlet 33 for leading the fuel gas out of the fuel cell stack 31.

In the fuel cell stack 31, the portion of the fuel gas flow that is closer to the fuel inlet portion 32 than the fuel outlet portion 33 is the fuel upstream portion 31u. On the other hand, in the fuel cell stack 31, the portion closer to the fuel outlet 33 than the fuel inlet 32 in the fuel gas flow is the fuel downstream portion 31d. In other words, the fuel cell stack 31 is divided into a fuel upstream portion 31u including the fuel inlet portion 32 and a fuel downstream portion 31d including the fuel outlet portion 33 when the whole is divided into two equal parts along the flow of the fuel gas. Be done.

The oxidant gas supply device 50 includes a blower 51 and a guide member 52. The blower 51 is a device for supplying air containing oxygen, which is an oxidant gas, to the fuel cell stack 31. The blower 51 sucks in air from the fuel cell stack 31 side and discharges air to the side opposite to the fuel cell stack 31.

The blower 51 is provided so as to face the fuel cell stack 31. The blower 51 includes an upstream blower 51u that blows air so as to pass through the fuel upstream portion 31u, and a downstream blower 51d that blows air so as to pass through the fuel downstream portion 31d. As the blower 51, an axial flow blower that blows air along the axial direction of the rotating shaft can be adopted. However, the blower 51 is not limited to an axial blower, and a centrifugal blower that blows air in the radial direction of the rotating shaft can also be adopted. Further, instead of the blower 51, air compressed by using a compressor may be supplied to the fuel cell stack 31.

The guide member 52 connects the blower 51 and the fuel cell stack 31 to form a flow path for the oxidant gas. The guide member 52 guides the oxidant gas to flow through the entire fuel cell stack 31 and suppresses the flow of wind without passing through the fuel cell stack 31. The guide member 52 is formed so that the air passage gradually becomes smaller from the fuel cell stack 31 toward the blower 51.

The fuel gas supply device 60 includes a fuel gas tank 61, a supply valve 62, and an exhaust valve 63. The fuel gas tank 61 is a tank that stores hydrogen gas, which is a fuel gas, in a high pressure state. The fuel gas tank 61 may be composed of a plurality of tanks. According to this, even if one tank becomes empty, the fuel gas can be continuously supplied from the other tank.

A supply valve 62 is provided in the fuel gas pipe connecting the fuel gas tank 61 and the fuel cell stack 31. The supply valve 62 is a valve device for adjusting the amount of fuel gas supplied from the fuel gas tank 61 to the fuel cell stack 31. By opening the supply valve 62, fuel gas is supplied to the fuel cell stack 31, and by closing the supply valve 62, the supply of fuel gas to the fuel cell stack 31 is stopped. The supply valve 62 is a solenoid valve whose opening degree can be electrically controlled. However, the supply valve 62 may be configured by a valve device other than the solenoid valve.

A discharge valve 63 is provided in the fuel gas pipe connecting the fuel cell stack 31 and the outside. The exhaust valve 63 is a valve device that adjusts the amount of exhaust gas discharged to the outside from the fuel cell stack 31 such as fuel gas that was not used in the reaction in the fuel cell stack 31. Here, the exhaust gas includes a gas other than the unreacted fuel gas. For example, the exhaust gas includes water vapor as water generated by a chemical reaction in the fuel cell stack 31. For example, the exhaust gas includes air that is supplied to the fuel cell stack 31 as an oxidant gas and partially leaks to the fuel gas side. By opening the discharge valve 63, the exhaust gas is discharged from the fuel cell stack 31, and by closing the discharge valve 63, the discharge of the exhaust gas from the fuel cell stack 31 is stopped. The discharge valve 63 is a solenoid valve whose opening degree can be electrically controlled. However, the discharge valve 63 may be configured by a valve device other than the solenoid valve.

When power is generated by the fuel cell stack 31, the supply valve 62 is opened to supply fuel gas to the fuel cell stack 31. Further, the exhaust valve 63 is kept closed until the supplied fuel gas is consumed, and when the consumption of the fuel gas is completed, the exhaust valve 63 is opened to discharge the exhaust gas. When the exhaust gas is discharged, the fuel gas is newly supplied into the fuel cell stack 31. However, the exhaust gas including the unreacted fuel gas may be discharged with the discharge valve 63 always open.

The unreacted fuel gas that has flowed through the fuel cell stack 31 may not be discharged as it is, but may be flown back into the fuel cell stack 31. According to this, the unreacted fuel gas can be recirculated in the fuel cell stack 31 and used for the chemical reaction. Therefore, the amount of fuel gas discharged without reaction can be reduced, and the fuel gas can be efficiently used for power generation. However, the size of the entire fuel cell system 1 tends to increase due to the addition of a configuration for recirculating the fuel gas. In other words, it is easy to design the size of the entire fuel cell system 1 to be small by not providing a configuration for recirculating the fuel gas. Therefore, it is preferable to select whether or not to adopt a configuration in which the fuel gas is recirculated in consideration of the application of the fuel cell system 1, the usage environment, and the like.

The fuel cell system 1 includes a load 81, a secondary battery 82, and a control unit 90. The load 81 is a device that consumes the electric power generated by the fuel cell stack 31. The load 81 is, for example, a traveling motor used for traveling a vehicle. The load 81 is, for example, a heater device used for hot water supply. The secondary battery 82 is a device that stores the electric power generated by the fuel cell stack 31. The load 81 may be driven by using the electric power stored in the secondary battery 82. The control unit 90 controls the drive of various devices constituting the fuel cell system 1 to control the power generation of the fuel cell stack 31.

In FIG. 2, the upstream blower 51u and the downstream blower 51d are provided adjacent to each other. Both the upstream blower 51u and the downstream blower 51d are axial blowers. The rotation shaft of the upstream blower 51u faces the fuel upstream portion 31u. The rotation shaft of the downstream blower 51d faces the fuel downstream portion 31d.

The fuel cell stack 31 is configured by stacking a plurality of fuel cell cells 11. The stacking direction of the fuel cell 11 is the Z direction. Here, the Z direction is the vertical direction, and both end surfaces of the fuel cell stack 31 in the Z direction correspond to the upper surface and the lower surface of the fuel cell stack 31. However, the stacking direction of the fuel cell 11 is not limited to the vertical direction. The blower 51 blows air in a direction intersecting the stacking direction of the fuel cell 11. The blowing direction of the blower 51 is the X direction. Here, the X direction coincides with the axial direction of the rotation axis of the blower 51. The direction orthogonal to the two directions in the X direction and the Z direction is the Y direction.

The fuel inlet portion 32 is provided on the lower surface of the fuel cell stack 31. Therefore, the fuel gas is introduced into the fuel cell stack 31 along the stacking direction of the fuel cell cells 11. The fuel outlet portion 33 is provided on the lower surface of the fuel cell stack 31. Therefore, the fuel gas is led out from the inside of the fuel cell stack 31 along the stacking direction of the fuel cell 11.

In FIG. 3, the fuel cell 11 includes a membrane electrode assembly 12, an oxidant gas diffusion layer 14a, a fuel gas diffusion layer 14b, a cathode separator 15, and an anode separator 16. The membrane electrode assembly 12 is a assembly in which an anode electrode is arranged on one surface of the electrolyte membrane and a cathode electrode is arranged on the other surface. The anode electrode and the cathode electrode are configured by supporting a catalyst such as platinum with a carrier such as carbon. The membrane electrode assembly 12 is also called MEA.

In each fuel cell 11, electric energy is output by supplying hydrogen gas that functions as a fuel gas and air containing oxygen that functions as an oxidant gas. More specifically, on the anode side, a reaction is triggered in which hydrogen is transformed into hydrogen ions and electrons. On the other hand, on the cathode side, a reaction is triggered in which hydrogen ions, electrons, and oxygen react to generate water.

The oxidant gas diffusion layer 14a and the fuel gas diffusion layer 14b have a function of diffusing a reaction gas such as an oxidant gas or a fuel gas. The oxidant gas diffusion layer 14a and the fuel gas diffusion layer 14b are composed of a porous member having gas permeability and electron conductivity.

The cathode separator 15 and the anode separator 16 are made of, for example, conductive carbon equipment. The cathode separator 15 forms a flow path through which the oxidant gas flows. In the cathode separator 15, the direction in which the oxidant gas flows is the X direction. The anode separator 16 forms a flow path through which the fuel gas flows. In the anode separator 16, the direction in which the fuel gas flows is the Y direction. The oxidant gas diffusion layer 14a is located between the cathode separator 15 and the membrane electrode assembly 12. The fuel gas diffusion layer 14b is located between the anode separator 16 and the membrane electrode assembly 12.

The membrane electrode assembly 12 includes a manifold 19 through which fuel gas can flow outside the portion that functions as a reaction surface on which a chemical reaction is triggered. The oxidant gas diffusion layer 14a and the fuel gas diffusion layer 14b are provided with a manifold 19 through which fuel gas can flow, outside the portion that functions as the diffusion layer. The cathode separator 15 includes a manifold 19 through which fuel gas can flow outside the portion forming the flow path through which the oxidant gas flows. The anode separator 16 includes a manifold 19 capable of flowing fuel gas in the Z direction, which is the stacking direction of the fuel cell 11, at the end of a portion forming a flow path through which the fuel gas flows.

The manifold 19 includes an upstream manifold 19u through which fuel gas immediately after being introduced from the fuel inlet portion 32 flows. The manifold 19 includes a downstream manifold 19d through which the fuel gas immediately before being led out from the fuel outlet 33 flows. The manifold 19 allows the fuel gas to pass through the plurality of fuel cell cells 11 and flow into the flow path of the fuel gas formed in the anode separator 16.

In FIG. 4, the cathode separator 15 is a corrugated plate member. The cathode separator 15 includes two types of flow paths, a reaction flow path 15r and a cooling flow path 15c, as a flow path for the oxidant gas. The reaction flow path portion 15r is a flow path portion in which the oxidant gas diffusion layer 14a side is open. The oxidant gas flowing through the reaction flow path portion 15r flows into the oxidant gas diffusion layer 14a and is used for the chemical reaction. On the other hand, the cooling flow path portion 15c is a flow path portion in which the side opposite to the oxidant gas diffusion layer 14a is open. The oxidant gas flowing through the cooling flow path portion 15c cannot flow into the oxidant gas diffusion layer 14a. However, the oxidant gas passes through the fuel cell 11 in the X direction. Therefore, it contributes to cooling the fuel cell 11. The reaction flow path portion 15r and the cooling flow path portion 15c are formed so as to be alternately arranged in the Y direction.

In FIG. 5, retained water W may be present inside the anode separator 16. The reason why the stagnant water W is generated will be described below. In the chemical reaction of the fuel cell 11, water is generated on the cathode side. Further, when air is supplied as an oxidant gas, the supplied air contains water. As described above, during the power generation of the fuel cell stack 31, water is present on the cathode separator 15 side. Further, the membrane electrode assembly 12 generates heat as the fuel cell stack 31 generates electricity. Therefore, the water present on the cathode separator 15 side is easily heated by the membrane electrode assembly 12 to become water vapor.

The electrolyte membrane constituting the membrane electrode assembly 12 is a membrane that allows not only hydrogen ions but also water vapor to permeate. Therefore, in the membrane electrode assembly 12, the water vapor existing on the cathode side passes through the membrane electrode assembly 12 and moves to the anode side. The phenomenon of water vapor moving from the cathode side to the anode side is called backdiffusion. The water vapor transferred to the anode side is cooled and condensed on the surface of the anode separator 16. When this condensed water stays on the surface of the anode separator 16, it becomes retained water W. Backdiffusion is more likely to occur in cows as the film thickness of the electrolyte membrane of the membrane electrode assembly 12 increases.

Further, in the fuel cell 11, a part of the oxidant gas flowing on the cathode side may leak to the anode side. Therefore, a part of the oxidant gas is mixed with the fuel gas flowing on the cathode side. When air is supplied as an oxidant gas, nitrogen, water, etc. leaked from the cathode side are mixed in the fuel gas. The water leaking from the cathode side can also be condensed on the surface of the anode separator 16 in the same manner as the water vapor that has passed through the membrane electrode assembly 12, and become retained water W.

The reverse diffusion of water vapor generated on the cathode side to the anode side and the phenomenon that a part of the oxidant gas leaks from the cathode side to the anode side can occur in the entire fuel cell 11. Therefore, in the flow of fuel gas, the more downstream the fuel gas is, the more water is likely to be mixed. Therefore, in the flow of the fuel gas flowing through the fuel cell 11, the stagnant water W is likely to be generated in the portion located downstream, and the amount of the stagnant water W is likely to increase.

The stagnant water W narrows the flow path of the fuel gas in the anode separator 16 and increases the pressure loss. In other words, the presence of the stagnant water W makes it difficult for the fuel gas to properly flow through the anode separator 16. Therefore, among the plurality of flow path portions formed in the anode separator 16, the flow path portion in which the stagnant water W exists has a smaller amount of fuel gas than the flow path portion in which the stagnant water W does not exist. Therefore, the fuel gas required for appropriate power generation cannot be supplied, and the amount of power generated in the fuel cell 11 is reduced. As described above, the amount of power generated by each fuel cell 11 varies depending on the presence or absence of the stagnant water W and the amount of the stagnant water W in each fuel cell 11, and the amount of power generated by the fuel cell stack 31 as a whole decreases.

The control for suppressing the influence of the accumulated water W in the fuel cell system 1 will be described below. In FIG. 6, the fuel cell stack 31 and the secondary battery 82 are connected to the control unit 90. The control unit 90 acquires information regarding power generation of the fuel cell stack 31. The control unit 90 controls the fuel cell stack 31 to control the amount of power generation. The control unit 90 acquires information such as the amount of electricity stored in the secondary battery 82. The control unit 90 controls the secondary battery 82 to control the amount of electricity stored.

A temperature sensor 86, a humidity sensor 87, and a voltage sensor 88 are connected to the control unit 90. The control unit 90 acquires information on the temperature of the fuel cell stack 31 measured by the temperature sensor 86. The control unit 90 acquires information on the humidity of the fuel cell stack 31 measured by the humidity sensor 87. The control unit 90 acquires information regarding the voltage of the fuel cell stack 31 measured by the voltage sensor 88.

The blower 51, the supply valve 62, and the discharge valve 63 are connected to the control unit 90. The control unit 90 controls the blower 51 to control the amount of oxidant gas flowing through the fuel cell stack 31. The control unit 90 controls the opening degree of the supply valve 62 to control the amount of fuel gas supplied to the fuel cell stack 31. The control unit 90 controls the opening degree of the discharge valve 63 to control the amount of exhaust gas discharged from the fuel cell stack 31.

In FIG. 7, when the control related to power generation in the fuel cell system 1 is started by an input operation by the user or the like, the battery voltage, which is the voltage of the fuel cell stack 31, is measured in step S101. As the battery voltage, the voltage of each of the plurality of fuel cell cells 11 can be measured to obtain the voltage of the entire fuel cell stack 31. However, instead of acquiring the voltages of all the fuel cell cells 11, the voltages of some fuel cell cells 11 may be acquired to estimate the voltage of the entire fuel cell stack 31. After measuring the battery voltage, the process proceeds to step S102.

In step S102, it is determined whether or not the battery voltage is equal to or higher than the threshold value. Here, the threshold value is set to a voltage lower than the battery voltage when power is appropriately generated in the fuel cell stack 31. If the measured battery voltage is equal to or higher than the threshold value, it is determined that power can be generated appropriately, and the process proceeds to step S111. On the other hand, if the measured battery voltage is less than the threshold value, it is determined that power generation may not be performed properly, and the process proceeds to step S130.

In step S111, the battery temperature, which is the temperature of the fuel cell stack 31, is measured. As the battery temperature, the temperature can be measured for each of the plurality of fuel cell cells 11 to obtain the temperature distribution of the entire fuel cell stack 31. However, instead of acquiring the temperatures of all the fuel cell cells 11, the temperature of some fuel cell cells 11 may be acquired to estimate the temperature of the entire fuel cell stack 31. After measuring the battery temperature, the process proceeds to step S112.

In step S112, it is determined whether or not the battery temperature is equal to or higher than the threshold value. Here, the threshold value is set to a temperature lower than the battery temperature when power is appropriately generated in the fuel cell stack 31. If the measured battery temperature is equal to or higher than the threshold value, it is determined that power generation can be appropriately performed, and the process proceeds to step S120. On the other hand, if the measured battery temperature is less than the threshold value, it is determined that power generation may not be performed properly, and the process proceeds to step S130.

In step S120, the fuel cell stack 31 is cooled in the normal mode. In the normal mode, the blower 51 is driven to supply the oxidant gas to the fuel cell stack 31. The amount of air blown by the blower 51 is at least such that the amount of oxygen required for the chemical reaction in the fuel cell stack 31 is not insufficient. In other words, the amount of air blown by the blower 51 may be the amount of air blown to supply an excess amount of oxygen that cannot be consumed by the chemical reaction. The upstream blower 51u and the downstream blower 51d are controlled at the same rotation speed, and the amount of air blown to the fuel upstream portion 31u and the amount of air blown to the fuel downstream portion 31d are equal. However, the upstream blower 51u and the downstream blower 51d do not have to have exactly the same air flow rate. As long as the oxygen gas required for power generation of the fuel cell stack 31 can be supplied, the upstream blower 51u and the downstream blower 51d may have different air amounts.

In the normal mode, the oxidant gas is actively introduced into both the fuel upstream portion 31u and the fuel downstream portion 31d. Therefore, the entire fuel cell stack 31 is actively air-cooled. The normal mode is a cooling mode in which the temperature of the fuel cell stack 31 is cooled substantially uniformly. In other words, the normal mode is a cooling mode in which the cooling performance of the fuel upstream portion 31u and the cooling performance of the fuel downstream portion 31d are maintained at the same level. After executing the normal mode, the process proceeds to step S141 while maintaining the normal mode.

In step S130, the fuel cell stack 31 is cooled in the stagnant water suppression mode. In the stagnant water suppression mode, the blower 51 is driven to supply the oxidant gas to the fuel cell stack 31. At this time, the temperature of the fuel downstream portion 31d is cooled so as to be higher than the temperature of the fuel upstream portion 31u. More specifically, the amount of air blown by the downstream blower 51d is made smaller than the amount of air blown by the upstream blower 51u.

In the stagnant water suppression mode, various methods can be adopted as a method for reducing the amount of air blown by the downstream blower 51d. For example, after adopting the same blower for the upstream blower 51u and the downstream blower 51d, the rotation speed of the downstream blower 51d may be driven and controlled to be lower than the rotation speed of the upstream blower 51u. For example, as the downstream blower 51d, a small blower having a smaller amount of air than the upstream blower 51u may be adopted. For example, the upstream blower 51u may be driven in continuous operation, and the downstream blower 51d may be driven in intermittent operation to shorten the blowing time to reduce the amount of air blown.

The temperature of the fuel cell stack 31 naturally rises due to heat generated by power generation. By executing the stagnant water suppression mode, the cooling performance of the fuel downstream portion 31d can be intentionally lowered, and the temperature rise due to the heat generated by the fuel cell stack 31 itself can be promoted. As a result, the temperature of the anode separator 16 at the downstream portion 31d of the fuel can be raised, and the generation of condensed water on the surface of the anode separator 16 can be suppressed. Alternatively, the retained water W remaining on the surface of the anode separator 16 can be evaporated and removed. After executing the stagnant water suppression mode, the process proceeds to step S141.

In step S141, it is determined whether or not there is a drive request for the fuel cell system 1. When it is necessary to continue power generation, such as when the load 81 consumes a large amount of power or when the amount of electricity stored in the secondary battery 82 is small, a drive request is made. On the other hand, when it is not necessary to continue power generation, there is no drive request. Whether or not there is a drive request can be switched by, for example, a user operation.

When there is no drive request, the supply valve 62 and the discharge valve 63 are closed, the drive of the blower 51 is stopped, and the control related to the power generation of the fuel cell system 1 is terminated. On the other hand, when there is a drive request, the process returns to step S101 and a series of controls is repeated until there is no drive request. This makes it possible to select an appropriate cooling mode by reflecting the state inside the fuel cell stack 31 that is constantly changing due to power generation.

According to the above-described embodiment, the control unit 90 controls the oxidant gas supply device 50 so that the temperature of the fuel downstream portion 31d is higher than the temperature of the fuel upstream portion 31u. Therefore, the temperature of the fuel downstream portion 31d, in which the amount of water contained in the fuel gas tends to be larger than that of the fuel upstream portion 31u, can be raised. In other words, the temperature of the fuel downstream portion 31d is configured to be higher than the temperature of the fuel upstream portion 31u. Therefore, it is easy to prevent the moisture in the fuel gas from condensing on the surface of the anode separator 16 to generate the retained water W. Therefore, it is possible to provide the fuel cell system 1 capable of stably generating electricity.

The control unit 90 controls the blower 51 so that the amount of air blown to the fuel downstream portion 31d is smaller than the amount of air blown to the fuel upstream portion 31u. Therefore, as compared with the case of using a blower such as an air compressor as a method of supplying the oxidant gas, it is easy to configure the structure to be smaller and lighter. Therefore, it is easy to design the oxidant gas supply device 50 to be small and reduce the size of the entire fuel cell system 1. In particular, in a fuel cell vehicle, it is required to install the fuel cell system 1 in a limited installation space. Alternatively, a high degree of freedom is required for the place where it can be installed so as to accommodate the installation space of various vehicle types. Therefore, it is very important to design the fuel cell system 1 as small as possible when the fuel cell system 1 is mounted on a vehicle.

The control unit 90 controls so that the amount of air blown by the downstream blower 51d is smaller than the amount of air blown by the upstream blower 51u. Therefore, the temperatures of the fuel upstream portion 31u and the fuel downstream portion 31d can be easily adjusted by properly using a plurality of blowers. Therefore, it is possible to stably cool the fuel upstream portion 31u and suppress excessive cooling of the fuel downstream portion 31d.

The control unit 90 controls the oxidant gas supply device 50 so that when the battery temperature is below the threshold value, the supply amount of the oxidant gas is smaller than when the battery temperature is above the threshold value. Therefore, when the battery temperature is low, the temperature of the anode separator 16 can be raised to evaporate the stagnant water W. Therefore, it is possible to eliminate the decrease in the amount of power generation due to the retained water W. Alternatively, stable power generation can be maintained in the entire fuel cell stack 31 by eliminating the state in which the temperature is low and the accumulated water W is likely to be generated. Since the judgment is based on the temperature, the influence of the stagnant water W can be suppressed before the condensed water starts to be generated and the battery voltage drops.

The control unit 90 controls the oxidant gas supply device 50 so that when the battery voltage is less than the threshold value, the supply amount of the oxidant gas is smaller than when the battery voltage is equal to or more than the threshold value. Therefore, when the battery voltage is low, the temperature of the anode separator 16 can be raised to evaporate the accumulated water W. Therefore, it is possible to eliminate the decrease in the amount of power generation due to the influence of the accumulated water W. Since the judgment is based on the voltage, it is possible to eliminate the decrease in the amount of power generation by evaporating the stagnant water W after confirming that the power generation is actually affected. In particular, by maintaining the stagnant water suppression mode until the battery voltage becomes equal to or higher than the threshold value, it is possible to prevent the stagnant water suppression mode from being released before the influence of the stagnant water W disappears.

The control unit 90 controls the cooling mode by using a plurality of types of physical quantities of the battery voltage and the battery temperature. Therefore, as compared with the case where the cooling mode is controlled based on only one type of physical quantity, the stagnant water suppression mode can be executed more accurately and the decrease in the power generation amount due to the stagnant water W can be suppressed.

Regardless of the voltage or temperature of the fuel cell stack 31, the amount of air blown by the downstream blower 51d may always be lower than the amount of air blown by the upstream blower 51u. In this case, the control unit 90 can be regarded as always driving the blower 51 in the stagnant water suppression mode.

Further, in both the normal mode and the accumulated water suppression mode, the amount of air blown by the downstream blower 51d may be lower than the amount of air blown by the upstream blower 51u. In this case, it is preferable that the air volume difference between the upstream blower 51u and the downstream blower 51d in the stagnant water suppression mode is larger than the air volume difference between the upstream blower 51u and the downstream blower 51d in the normal mode. According to this, even in the normal mode, the stagnant water W can be evaporated by executing the stagnant water suppression mode when the stagnant water W is generated while suppressing the generation of the stagnant water W to some extent.

Second Embodiment This embodiment is a modification based on the preceding embodiment. In this embodiment, the rotating shaft of the blower 251 faces the fuel upstream portion 31u.

In FIG. 8, the oxidant gas supply device 250 includes a blower 251 and a guide member 252. The blower 251 is an axial blower that blows air along the axial direction of the rotating shaft. The rotating shaft of the blower 251 faces the second portion counting from the upstream side when the fuel cell stack 31 is divided into four equal parts along the flow of fuel gas. At this position, the entire blower 251 faces the first to third parts of the fuel cell stack 31, which is divided into four equal parts, counting from the upstream side of the fuel gas flow, and is the fourth. The positional relationship is such that only the parts do not face each other.

The guide member 252 connects the blower 251 and the fuel cell stack 31 to form a flow path for the oxidant gas. The guide member 252 guides the oxidant gas to flow through the entire fuel cell stack 31 and suppresses the flow of wind without passing through the fuel cell stack 31. The guide member 252 is formed so that the air passage gradually becomes smaller from the fuel cell stack 31 toward the blower 51.

In the flow path of the oxidant gas formed by the guide member 252, the distance from the fuel downstream portion 31d to the blower 251 is longer than the distance from the fuel upstream portion 31u to the blower 251. Therefore, the amount of the oxidant gas supplied to the fuel downstream portion 31d tends to be smaller than the amount of the oxidant gas supplied to the fuel upstream portion 31u. It is preferable to control the rotation speed of the blower 251 so that more oxygen than necessary for the chemical reaction is supplied, based on the portion where the amount of air blown is most likely to be small.

According to the above-described embodiment, the blower 251 is provided at a position where the rotating shaft faces the fuel upstream portion 31u. Therefore, when the control unit rotates and drives the blower 251, the amount of air blown to the fuel upstream portion 31u can be automatically increased to be larger than the amount of air blown to the fuel downstream portion 31d. Therefore, the temperature of the fuel downstream portion 31d tends to be higher than the temperature of the fuel upstream portion 31u.

By controlling one blower 251 the amount of air blown to the fuel upstream portion 31u can be made larger than the amount of air blown to the fuel downstream portion 31d. In other words, the control of one blower 251 can cause a temperature difference depending on the portion of the fuel cell stack 31. Therefore, the number of parts can be reduced as compared with the case where the amount of air blown is controlled by using a plurality of blower devices.

Third Embodiment This embodiment is a modification based on the preceding embodiment. In this embodiment, a pressure drop body 353 is provided between the blower 351 and the fuel downstream portion 31d.

In FIG. 9, the oxidant gas supply device 350 includes a blower 351, a guide member 52, and a pressure drop body 353. The blower 351 is an axial blower. The rotating shaft of the blower 351 faces a portion between the fuel upstream portion 31u and the fuel downstream portion 31d.

A pressure drop body 353 is provided inside the guide member 52 between the blower 351 and the fuel downstream portion 31d. The pressure loss body 353 is a component that hinders the smooth flow of the oxidant gas and intentionally causes a pressure loss. The pressure drop body 353 may be a component that does not completely block the space between the blower 351 and the fuel downstream portion 31d. As the pressure drop body 353, a mesh-like part can be adopted. As the pressure drop body 353, a component having a plurality of slits formed in the plate can be adopted. As the pressure drop body 353, a cloth having breathability can be adopted. As the pressure drop body 353, a damper device capable of controlling the size of the flow path area by opening and closing can be adopted.

The pressure drop body 353 is provided at a portion where the blower 351 and the fuel downstream portion 31d face each other. As a result, the amount of oxidant gas sucked from the portion of the blower 351 facing the downstream portion 31d of the fuel is reduced. Therefore, the amount of air blown to the fuel downstream portion 31d is smaller than the amount of air blown to the fuel upstream portion 31u. By changing the size and shape of the pressure drop body 353, the amount of air blown to the fuel downstream portion 31d can be adjusted. For example, by increasing the size of the pressure drop body 353, the pressure loss generated by the pressure drop body 353 can be increased. As a result, the amount of air blown to the fuel downstream portion 31d can be reduced.

According to the above-described embodiment, a pressure drop body 353 that suppresses the flow of the oxidant gas is provided between the blower 351 and the fuel downstream portion 31d. Therefore, the amount of air blown to the fuel downstream portion 31d can be made smaller than the amount of air blown to the fuel upstream portion 31u. In particular, the amount of air blown to the fuel downstream portion 31d can be easily controlled by appropriately changing the size, position, material, and the like of the pressure drop body 353.

The pressure drop body 353 is located upstream of the blower 351 in the flow of the oxidant gas. Therefore, the pressure drop body 353 receives a force in the direction approaching the blower 351 by the blower of the blower 351. Therefore, the pressure drop body 353 is not blown away from the blower 351 by the blower of the blower 351.

As the pressure drop body 353, a screw member for fastening and fixing the fuel cell 11 in a laminated state may be adopted. According to this, the screw member which is the pressure loss body 353 can be provided with two functions, that is, a function of causing a pressure loss and a function of fixing the fuel cell 11s to each other. Therefore, it is not necessary to provide a dedicated part for the purpose of causing a pressure loss.

As the pressure drop body 353, a physical quantity sensor that measures a physical quantity related to the fuel cell stack 31 may be adopted. The physical quantity sensor measures physical quantities such as temperature and humidity that change with the power generation of the fuel cell stack 31. According to this, the physical quantity sensor, which is the pressure loss body 353, can be provided with two functions, that is, a function of causing a pressure loss and a function of measuring the physical quantity of the fuel cell stack 31. Therefore, it is not necessary to provide a dedicated part for the purpose of causing a pressure loss. As the physical quantity sensor, different types of sensors such as the temperature sensor 86 and the humidity sensor 87 may be installed as the pressure drop body 353. Alternatively, a plurality of sensors of the same type may be installed as the pressure drop body 353 by providing a temperature sensor 86 for each of the plurality of fuel cell cells 11.

Another Embodiment Although the case where one fuel cell stack 31 is divided into two parts, the fuel upstream part 31u and the fuel downstream part 31d, has been described as an example, the fuel gas flow is divided into the upstream side and the downstream side. Two different fuel cell stacks 31 may be arranged side by side. In this case, the fuel cell stack 31 on the upstream side corresponds to the fuel upstream portion 31u, and the fuel cell stack 31 on the downstream side corresponds to the fuel downstream portion 31d.

Disclosure in this specification, drawings and the like is not limited to the illustrated embodiments. The disclosure includes exemplary embodiments and modifications by those skilled in the art based on them. For example, disclosure is not limited to the parts and / or element combinations shown in the embodiments. Disclosure can be carried out in various combinations. The disclosure can have additional parts that can be added to the embodiments. Disclosures include those in which the parts and / or elements of the embodiment are omitted. Disclosures include replacements or combinations of parts and / or elements between one embodiment and the other. The technical scope disclosed is not limited to the description of the embodiments. Some technical scopes disclosed are indicated by the claims description and should be understood to include all modifications within the meaning and scope equivalent to the claims statement.

Disclosure in the description, drawings, etc. is not limited by the description of the scope of claims. The disclosure in the description, drawings, etc. includes the technical ideas described in the claims, and further covers a wider variety of technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure of the description, drawings, etc. without being bound by the description of the claims.

The control unit and its method described in the present disclosure may be realized by a dedicated computer constituting a processor programmed to perform one or more functions embodied by a computer program. Alternatively, the apparatus and method thereof described in the present disclosure may be realized by a dedicated hardware logic circuit. Alternatively, the apparatus and method thereof described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor that executes a computer program and one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transitional tangible recording medium as an instruction executed by the computer.

1 fuel cell system, 11 fuel cell, 12 membrane electrode junction, 15 cathode separator, 16 anode separator, 19 manifold, 31 fuel cell stack, 31u fuel upstream, 31d fuel downstream, 32 fuel inlet, 33 fuel outlet , 50 Oxidizing agent gas supply device, 51 blower, 51u upstream blower, 51d downstream blower, 52 guide member, 60 fuel gas supply device, 61 fuel gas cylinder, 62 supply valve, 63 discharge valve, 86 temperature sensor, 87 humidity sensor, 88 voltage sensor, 90 control unit, 250 oxidant gas supply device, 251 blower, 252 guide member, 350 oxidant gas supply device, 351 blower, 353 pressure loss

Claims (8)

A fuel cell stack (31) that generates electricity through a chemical reaction between fuel gas and oxidant gas, and
A fuel gas supply device (60) for supplying fuel gas to the fuel cell stack, and
An oxidant gas supply device (50, 250, 350) that supplies the oxidant gas to the fuel cell stack and cools the fuel cell stack.
A control unit (90) for controlling the power generation of the fuel cell stack is provided.
The fuel cell stack
A fuel inlet (32) for introducing fuel gas into the fuel cell stack, and
A fuel outlet (33) for deriving the fuel gas from the inside of the fuel cell stack, and
Of the fuel cell stack, the fuel upstream portion (31u), which is a portion closer to the fuel inlet portion than the fuel outlet portion, and
The fuel cell stack includes a fuel downstream portion (31d) which is a portion closer to the fuel outlet portion than the fuel inlet portion.
The control unit is a fuel cell system that controls the oxidant gas supply device so that the temperature of the fuel downstream portion becomes higher than the temperature of the fuel upstream portion. The oxidant gas supply device includes a blower (51) that sends air.
The fuel cell system according to claim 1, wherein the control unit controls the blower so that the amount of air blown to the downstream part of the fuel is smaller than the amount of air blown to the upstream part of the fuel. The blower
An upstream blower (51u) that blows air to the upstream part of the fuel, and
It is equipped with a downstream blower (51d) that blows air to the downstream portion of the fuel.
The fuel cell system according to claim 2, wherein the control unit controls the amount of air blown by the downstream blower to be smaller than the amount of air blown by the upstream blower. The blower is an axial blower that blows air along the axial direction of the rotating shaft.
The fuel cell system according to claim 2, wherein the axial blower is provided at a position where the rotating shaft faces the upstream portion of the fuel. The fuel cell system according to any one of claims 2 to 4, further comprising a pressure drop body (353) that suppresses the flow of an oxidant gas between the blower and the downstream portion of the fuel. The fuel cell system according to claim 5, wherein the pressure drop body is a physical quantity sensor that acquires a physical quantity. A temperature sensor (86) for measuring the battery temperature, which is the temperature of the fuel cell stack, is provided.
The control unit controls the oxidant gas supply device so that when the battery temperature is below the threshold value, the supply amount of the oxidant gas is smaller than when the battery temperature is above the threshold value. The fuel cell system according to any one of 1 to 6. A voltage sensor (88) for measuring the battery voltage, which is the voltage of the fuel cell stack, is provided.
The control unit controls the oxidant gas supply device so that when the battery voltage is less than the threshold value, the supply amount of the oxidant gas is smaller than when the battery voltage is equal to or more than the threshold value. The fuel cell system according to any one of 1 to 7.

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