JP4796358B2 - Fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system, particularly, the invention relates to a fuel cell system for discharging the water generated in the system to the outside.

  In recent years, solid polymer fuel cells have attracted attention as power sources for electric vehicles. A polymer electrolyte fuel cell is configured by stacking cells in which a polymer electrolyte membrane is sandwiched between a pair of electrodes (anode electrode and cathode electrode). In a fuel cell system equipped with this fuel cell, hydrogen (fuel gas) supplied to the anode electrode is hydrogen ionized in the catalyst layer and emits electrons. These electrons are taken out when flowing through an external circuit toward the cathode and are used as direct current electric energy. The hydrogen ions move to the cathode electrode through the solid polymer electrolyte membrane, and water is generated by combining oxygen (oxidant gas) supplied to the cathode electrode and electrons that have reached through the external circuit. The

  By the way, since the solid polymer electrolyte membrane needs an appropriate humidity to maintain its ion permeability, hydrogen and oxygen are supplied to the fuel cell in an appropriately humidified state. For this reason, the off gas from the fuel cell contains a large amount of moisture that has not been absorbed by the solid polymer electrolyte membrane and moisture as a reaction product, and when this off gas is cooled, condensation occurs in the gas flow path. Thus, when the generated water flows through the gas flow path into the fuel cell and adheres to the solid polymer electrolyte membrane, the power generation efficiency of the fuel cell is significantly reduced.

  Thus, conventionally, a fuel cell system including a gas-liquid separator in a gas flow path has been proposed (see, for example, Patent Document 1). FIG. 6 is a time chart showing a water level discharge image (upper stage) and a drain valve open / closed state (lower stage) when performing a conventional drainage control process.

The gas-liquid separator condenses water in the gas flow path to separate the gas and liquid, and stores this water in a tank, so that the water in the gas flow path does not flow into the fuel cell. Yes. Here, the drainage from the tank is performed by opening the drain valve. However, the drain valve is opened after the pressure rises due to the supply of hydrogen gas, as shown in FIG. This is to prevent air from flowing into the anode system as the drain valve opens.
Japanese Patent Laying-Open No. 2005-19304 (paragraph 0048, FIG. 6)

  However, when a large amount of condensed water is generated when the system is stopped, the water overflowed in the gas-liquid separator may flow into the fuel cell due to the supply of hydrogen gas. As a result, there is a problem that power generation stability is deteriorated and drivability as a vehicle is impaired.

  On the other hand, if the drain valve is always opened when the system is stopped in order to prevent water from accumulating in the gas-liquid separator, there is a problem that air flows into the anode system.

The present invention solves the problems mentioned above, to prevent the inflow of water into the fuel cell, and to provide a fuel cell system that can prevent deterioration of the power generation stability.

In order to solve the above-described problems, the present invention provides a fuel cell that generates electric power by being supplied with an oxidant gas and a fuel gas, and a drain means disposed in a flow path of the fuel gas connected to the fuel cell. a water storage amount grasping means for grasping the water volume of the drainage means at system startup, before the supply of the fuel gas to pre-Symbol fuel cell, based on the water volume of the water volume detection means is grasped, by the drainage means Drainage control means for controlling wastewater treatment , wherein the drainage means is a gas-liquid separator having a tank for storing water separated from the flow path of the fuel gas and a drain valve provided in the tank. The drainage control means controls the wastewater treatment by changing the valve opening time of the drain valve before supplying the fuel gas in accordance with the water storage amount grasped by the water storage amount grasping means. The amount grasping means grasps the water storage amount based on the system stop time, and the drainage control means does not open when the system stop time is less than the first predetermined time, and does not open the first predetermined time. When the time is longer than the time, the longer the system stop time, the longer the opening time of the drain valve .

According to the present invention, the drainage control means controls the wastewater treatment by the drainage means based on the water storage amount grasped by the water storage amount grasping means before the supply of the fuel gas to the fuel cell. According to this, since the drainage control means controls the drainage treatment based on the amount of stored water before the fuel gas is supplied, the water overflowed from the drainage means is prevented from flowing into the fuel cell by the supply of the fuel gas. Can be prevented.
The drainage control means controls the drainage treatment by changing the valve opening time of the drain valve. That is, when the amount of stored water is large, the valve opening time is lengthened, and when the amount of stored water is small, the valve opening time is shortened or not controlled. According to this, waste water treatment can be simplified.
The stored water amount grasping means grasps the stored water amount based on the system stop time. In other words, the longer the system has been stopped, the more condensed water is generated in the fuel gas flow path, so the amount of stored water is estimated to be large. According to this, it is possible to easily grasp the water storage amount without using a sensor or the like.
It is preferable that the drainage control means controls the wastewater treatment by the drainage means based on the grasped water storage amount and the storage capacity of the tank. According to this, since it is possible to grasp when the amount of stored water exceeds the storage capacity of the tank or when the water is full, it is possible to appropriately control the waste water treatment.

Further, the drainage control means is configured so that when the system stop time exceeds a second predetermined time that is later than the first predetermined time, a certain amount of water stored in the tank remains. The drain valve is opened for a certain time .

According to the fuel cell system according to the present invention, prior to the fuel gas supply to the fuel cell, it is possible to discharge the water in the water discharge means. Therefore, it is possible to prevent the water overflowing from the discharge means from flowing into the fuel cell along the flow of the fuel gas when the fuel gas is supplied. As a result, deterioration of power generation stability can be suppressed and drivability as a vehicle can be improved.

[First Embodiment]
Embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a schematic configuration diagram of a fuel cell system according to the present embodiment.

(Fuel cell system)
The fuel cell system S according to the present embodiment is used as a power source for an electric vehicle. The fuel cell 1, the compressor 2 that supplies air (oxidant gas) containing oxygen to the fuel cell 1, and the fuel cell 1 Hydrogen tank 3 for supplying hydrogen gas (fuel gas), gas-liquid separator 4 for separating water in hydrogen gas (hydrogen offgas) discharged from fuel cell 1, and hydrogen gas discharged from fuel cell 1 are diluted. The ECU 5 is mainly configured with a diluter 5 that discharges to the atmosphere and an ECU 6 that is a control unit.

  The fuel cell 1 is configured by stacking a plurality of cells each having a solid polymer electrolyte membrane 13 as an electrolyte sandwiched between an anode 11 and a cathode 12 (only a single cell is shown in FIG. 1). When hydrogen gas is supplied to the gas flow path 11a on the anode electrode 11 side of the fuel cell 1 and air is supplied to the gas flow path 12a on the cathode electrode 12 side, hydrogen ions generated in the catalyst layer of the anode electrode 11 are solid. It moves to the cathode electrode 12 through the polymer electrolyte membrane 13 and is combined with oxygen on the cathode electrode 12 side to generate water and to generate power in a single cell. The water generated on the cathode 12 side passes through the solid polymer electrolyte membrane 13 and also flows into the anode 11 side.

Hereinafter, each configuration of the fuel cell system S will be described along the flow of air or hydrogen gas supplied to the fuel cell 1.
The compressor 2 is a machine that compresses air, and the air compressed by the compressor 2 is supplied to the gas passage 12 a on the cathode electrode 12 side of the fuel cell 1 through the air supply passage 21. Further, the excess air (hereinafter referred to as “air off gas”) that cannot be chemically reacted among the air supplied into the fuel cell 1 is discharged to the diluter 5 to be described later via the air discharge passage 22. Is done.

The hydrogen tank 3 is a tank that stores high-pressure hydrogen, and hydrogen gas released from the hydrogen tank 3 passes through the hydrogen gas supply channel 31 to the gas channel 11 a on the anode electrode 11 side of the fuel cell 1. Supplied. In the hydrogen gas supply channel 31, a shutoff valve 31a, a regulator 31b, and an ejector 31c are arranged in this order from the upstream side. The shut-off valve 31a is a valve provided for releasing hydrogen gas from the hydrogen tank 3, and the regulator 31b is a valve for adjusting the pressure of the released hydrogen gas. The ejector 31c connects the hydrogen gas supply channel 31 and a hydrogen gas circulation channel 33, which will be described later, and mixes the hydrogen from the hydrogen tank 3 with the hydrogen discharged from the fuel cell 1 and returned to the fuel cell 1. To supply.
The air supply channel 21 and the hydrogen gas supply channel 31 are provided with a humidifier (not shown), and the air and hydrogen gas are supplied to the fuel cell 1 in an appropriately humidified state. The reason why the hydrogen gas and air are humidified is to maintain the ion permeability of the solid polymer electrolyte membrane 13.

  Of the hydrogen gas supplied into the fuel cell 1, hydrogen gas containing excess hydrogen that has not been chemically reacted (hereinafter referred to as “hydrogen offgas”) is discharged to the hydrogen gas discharge passage 32. The downstream side of the hydrogen gas discharge channel 32 is branched into a hydrogen gas circulation channel 33 and a hydrogen gas purge channel 34, and the hydrogen off-gas returns to the hydrogen gas supply channel 31 through the hydrogen gas circulation channel 33. Then, it is reused or discharged to the diluter 5 through the hydrogen gas purge flow path 34.

  The gas-liquid separator 4 is disposed in the hydrogen gas circulation flow path 33 and includes a tank 41 and a drain valve 42. The water separated from the hydrogen off gas is stored in the tank 41. Further, when a predetermined amount or more of water is stored in the tank 41, the drain valve 42 can be opened to drain the water to the outside. As described above, the water in the hydrogen off-gas is separated and drained by the gas-liquid separator 4 because the water flows into the fuel cell 1 through the gas flow path, adheres to the solid polymer electrolyte membrane 13 and is fueled. This is to prevent the power generation efficiency of the battery 1 from decreasing.

  The diluter 5 is connected to the downstream side of the hydrogen gas purge flow path 34 and the air discharge flow path 22. In the diluter 5, the hydrogen off-gas introduced from the hydrogen gas purge flow path 34 is replaced with the air off-gas introduced from the air discharge flow path 22 by intermittently opening a purge valve 34 a provided in the hydrogen gas purge flow path 34. Dilute and discharge to the outside. As a result, the hydrogen off-gas containing a large amount of impurities such as nitrogen is discharged to the outside through circulation.

  The ECU 6 includes a CPU, a RAM, a ROM, and an input / output circuit, and mainly estimates the water level in the tank 41 based on an output signal from the ignition switch 7 and a timer 8 that measures the system stop time. In addition to controlling the opening and closing of the drain valve 42, the compressor 2, the shutoff valve 31 a, the regulator 31 b, the ejector 31 c, the purge valve 34 a and the like are controlled for the operation of the fuel cell 1. Here, the system stop time means the time from when the ignition switch 7 is turned off to when it is turned on.

  Here, a method for estimating the water level in the tank 41 in the ECU 6 and a method for setting the valve opening time of the drain valve 42 will be described with reference to the drawings. In the drawings to be referred to, FIG. 2 is a map diagram showing the relationship between the system stop time and the estimated water level, and FIG. 3 is a map diagram showing the relationship between the system stop time and the valve opening time.

  First, the water level in the tank 41 can be estimated from the system stop time acquired from the timer 8. That is, as shown in FIG. 2, the estimated water level increases proportionally as the system shutdown time increases, and becomes constant when the system shutdown time exceeds a predetermined time. The reason why the estimated water level is proportionally increased is that the tank 41 is located at a low position, and the longer the system stop time, the more condensed water collects from each place (even from a distance). In addition, the estimated water level having a constant value means that the condensed water generated in each place has almost gathered. Note that the estimated water level with respect to the system stop time is appropriately changed depending on the shape of the tank 41 and the water storage capacity.

  Based on the relationship between the system stop time and the estimated water level (see FIG. 2), the ECU 6 sets the valve opening time of the drain valve 42 based on the map diagram shown in FIG. In the map diagram shown in FIG. 3, when the system stop time is less than the predetermined time t1 (short time), the valve is not opened. This is because, in the first place, the generated dew condensation water is small and there is no possibility that the water in the tank 41 flows into the fuel cell 1 side, so that the waste water treatment is unnecessary. Moreover, if the valve is opened in a state where the water level is low, air will flow into the anode system. Thereby, the starting time of the fuel cell 1 can be shortened. In addition, when the system stop time is between t1 and t2, the longer the system stop time, the longer the valve opening time. This is because the amount of water corresponding to the water level in the tank 41 is discharged. When the system stop time exceeds t2, the valve opening time is set to a fixed time. This is to prevent all the water in the tank 41 from being discharged.

  The map in FIG. 3 uses the system stop time as a parameter, but the system stop time corresponds in proportion to the estimated water level as described above. Therefore, even when the estimated water level is used as a parameter, the valve opening time is It is a map figure which shows the same relationship. That is, the valve opening time can be calculated directly from the system stop time, or the water level can be estimated from the system stop time (map diagram of FIG. 2), and the valve opening time can be calculated from the estimated water level value. In addition, the estimated water level at which the drain valve 42 needs to be opened (necessity of drainage) can be changed as appropriate. For example, it can be set that the tank 41 is drained in a full state, 80% water level, 50% water level, or the like. In the ECU 6 of this embodiment, the function of detecting the system stop time corresponds to the water storage amount grasping means of [Claims], and controls the opening / closing of the drain valve 42 (whether opening / closing, opening / closing time, etc.). The function corresponds to the drainage control means of [Claims].

  Next, the waste water treatment procedure of the gas-liquid separator 4 in the fuel cell system S will be described with reference to the drawings. In the drawings to be referred to, FIG. 4 is a flowchart of the drainage control process of the gas-liquid separator in the fuel cell system.

The drainage control process in the fuel cell system S is a process that is performed after the ignition switch 7 is turned on and before hydrogen gas is supplied to the fuel cell 1.
In the ECU 6 of the fuel cell system S, first, as shown in FIG. 4, when the ignition switch 7 (see FIG. 1) is turned on (step S1), the system stop time is set from the timer 8 (see FIG. 1). It is acquired and it is determined whether the fuel cell system S has been stopped for a predetermined time or more (step S2). As a result, when the system stop time is less than the predetermined time (No in step S2), the process proceeds to step S6. On the other hand, when the system stop time is equal to or longer than the predetermined time (Yes in step S2), the valve opening time of the drain valve 42 is set based on the map shown in FIG. 3 (step S3).

  Then, the drain valve 42 is opened (step S4), and it is monitored whether the set opening time of the drain valve 42 has elapsed (step S5). If the valve opening time has not elapsed (No in step S5), the monitoring in step S5 is repeated until the valve opening time is reached. On the other hand, when the valve opening time has elapsed (Yes in step S5), the drain valve is closed (step S6), and the drainage control process is terminated. Thereafter, supply of hydrogen gas to the fuel cell 1 is started.

  Next, the water level discharge state in the drainage control process in the fuel cell system S will be described with reference to the drawings. In the drawings to be referred to, FIG. 5 is a time chart showing a water level discharge image (upper stage) and an open / closed state of the drain valve (lower stage) when performing the drainage control process.

FIG. 5 assumes a case where the system stop time is long and a large amount of condensed water is accumulated in the tank 41 when the system is started.
In the present embodiment, as shown in FIG. 5, the drainage control process is performed after the ignition switch 7 is turned on and before the supply of hydrogen gas. Specifically, the drain valve 42 is opened for a predetermined time (valve opening request time), and the water in the tank 41 is discharged. Thereafter, the drain valve 42 is periodically opened, so that water is periodically discharged from the tank 41. Thereby, the water overflowed in the tank 41 is prevented from flowing into the fuel cell 1 due to the supply of hydrogen gas. In order to prevent the intrusion of outside air, a certain amount of water is left in the tank 41 and is not drained.

According to the above, the following effects can be obtained in the fuel cell system S according to the present embodiment.
In this embodiment, since the drainage control process is performed based on the water level in the tank 41 before the supply of hydrogen gas, the water overflowed in the tank 41 when the system is stopped flows into the fuel cell 1 by the supply of hydrogen gas. Can be prevented. As a result, the time required for stable power generation can be shortened, and drivability as a vehicle can be improved.

  In the present embodiment, when the system stop time is less than the predetermined time based on the water level in the tank 41, the drain valve 42 is not required to be opened. Startup time can be shortened.

Although the present embodiment has been described above, the present invention is not limited to the above-described embodiment, and can be implemented in various forms.
For example, in this embodiment, the system is configured not to drain when the system stop time is less than the predetermined time. However, the present invention is not limited to this, and even when the system stop time is short, it corresponds to that time. You may comprise so that the amount of water which drained may be drained from the inside of the tank 41. FIG.

  For example, in the present embodiment, the water level in the tank 41 is grasped based on the system stop time. However, the present invention is not limited to this, and the water level is detected by a water level sensor provided in the tank 41. It can also be configured. According to this, an accurate water level can be grasped.

  For example, in this embodiment, the drainage treatment of the tank 41 is controlled by adjusting the valve opening time. However, the present invention is not limited to this, and the drainage treatment is performed by adjusting the opening of the drain valve 42. It can also be set as the structure which controls.

  For example, in the present embodiment, the gas-liquid separator 4 is provided as the drainage means, but the present invention is not limited to this, and a drain valve may be provided in a drain pipe extending in the vertical direction. According to this, the drainage means can be configured easily.

1 is a schematic configuration diagram of a fuel cell system according to an embodiment. It is a map figure which shows the relationship between a system stop time and an estimated water level. It is a map figure which shows the relationship between system stop time and valve opening time. It is a flowchart of the waste_water | drain control process of the gas-liquid separator in a fuel cell system. It is a time chart which shows the water level discharge image (upper stage) at the time of performing drainage control processing, and the open / closed state (lower stage) of a drain valve. It is a time chart which shows the water level discharge image at the time of performing the conventional waste_water | drain control process (upper stage), and the open / closed state (lower stage) of a drain valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Compressor 3 Hydrogen tank 4 Gas-liquid separator 6 ECU
DESCRIPTION OF SYMBOLS 11 Anode electrode 12 Cathode electrode 13 Solid polymer electrolyte membrane 31 Hydrogen gas supply flow path 32 Hydrogen gas discharge flow path 33 Hydrogen gas circulation flow path 34 Hydrogen gas purge flow path 41 Tank 42 Drain valve S Fuel cell system

Claims (2)

A fuel cell that generates electricity by being supplied with an oxidant gas and a fuel gas; and
Drainage means disposed in the flow path of the fuel gas connected to the fuel cell;
A water storage amount grasping means for grasping a water storage amount of the drainage means when the system is started ; and
Before the supply of the fuel gas to pre-Symbol fuel cell, based on the water volume of the water volume detection means is grasped, and a discharge control means for controlling the waste water treatment by the effluent means,
The drainage means is a gas-liquid separator having a tank for storing water separated from the flow path of the fuel gas and a drain valve provided in the tank,
The drainage control means controls the wastewater treatment by changing the valve opening time of the drainage valve before supplying the fuel gas according to the water storage amount grasped by the water storage amount grasping means,
The water storage amount grasping means grasps the water storage amount based on a system stop time,
The drain control means does not open when the system stop time is less than the first predetermined time, and when the system stop time is longer than the first predetermined time, the drain control means opens the drain valve longer. A fuel cell system characterized by lengthening the valve time. The drain control means opens the drain valve so that a certain amount of water stored in the tank remains when the system stop time exceeds a second predetermined time longer than the first predetermined time. 2. The fuel cell system according to claim 1, wherein the valve time is set to a fixed time.

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