WO2008090430A1

WO2008090430A1 - Drainage apparatus for fuel cell system generation water

Info

Publication number: WO2008090430A1
Application number: PCT/IB2008/000096
Authority: WO
Inventors: Junichi Hasegawa; Ken Nakayama; Masaru Okamoto; Ryoichi Shimoi; Hidetaka Nishimura
Original assignee: Nissan Motor Co., Ltd.
Priority date: 2007-01-22
Filing date: 2008-01-16
Publication date: 2008-07-31

Abstract

A drainage apparatus (15) for draining water within a fuel cell system, the fuel cell system having a fuel cell (1) for generating electric power by electrochemically reacting a fuel gas with an oxidizer gas. A water reserving device (16) reserves a generation water resulting from reacting the fuel gas with the oxidizer gas. A drainage flow path (L13, L 14) discharges the generation water within the water reserving device from an end opened to an outside of the water reserving device. An opening/closing valve (17) is installed in the drainage flow path. A pressure adjusting device adjusts an inner pressure of the water reserving device. A controller (30) controls the opening/closing valve and the pressure adjusting device, such that the controller controls the opening/closing valve from a closed state to an opened state, in a state of decompressing the inner pressure of the water reserving device by the pressure adjusting device when the fuel cell system is stopped.

Description

DRAINAGE APPARATUS FOR FUEL CELL SYSTEM GENERATION WATER

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2007-11849, filed January 22, 2007, and Japanese Patent Application No. 2007-11853, filed January 22, 2007, the disclosures of which are incorporated by reference herein in the entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention The present invention relates to a drainage apparatus. In particular, the present invention relates to an apparatus for draining generation water resulting from the generation of electric power out of a fuel cell system that includes a fuel cell for generating electric power by electrochemically reacting a fuel gas with an oxidizer gas.

2. Description of the Related Art Japanese Laid-Open Patent Publication No. 2006-32134 discloses a fuel cell system, wherein a drainage apparatus with a water reserving function is installed in a fuel gas discharging flow path, and generation water resulting from a generation of a fuel cell is discharged to the outside by the drainage apparatus. A liquid water drainage pipe in an ejector structure having a suctioning port in a position equal to or less than a maximum water level of reserving water is connected to a gas discharging pipe having a gas inlet and a gas discharging valve in a position higher than the maximum water level of the reserving water. A jet pump effect is generated by the discharging gas flowing via a discharging pipe for air when opening the discharging valve. Further, since the reserving water is sucked into the liquid water discharging pipe, the reserving water can be discharged to the outside. Also, in the drainage apparatus, water remaining in the discharging valve by the discharging gas is blown out in order to pass the discharging gas through the discharging valve. To this end, when the system is stopped, the discharging valve is prevented from being frozen due to a decrease of external temperature.

However, when blowing out the water in the discharging valve, it is necessary to spill out the fuel gas discharged from the fuel cell in order to obtain the jet pump effect. To this end, according to such a method, there is a disadvantage in that a large amount of the fuel gas, which is not used in the generation of the electric power, is discharged to the outside.

The present invention is devised in consideration of the above circumstances. The object of the present invention is prevent freezing of an opening/closing device such as a valve while preventing a discharge of extra gas.

SUMMARY OF THE INVENTION

In order to solve the above problem, in an embodiment, the invention provides a drainage apparatus for draining water within a fuel cell system, the fuel cell system having a fuel cell for generating electric power by electrochemically reacting a fuel gas with an oxidizer gas. A water reserving device reserves a generation water resulting from reacting the fuel gas with the oxidizer gas. A drainage flow path discharges the generation water within the water reserving device from an end opened to an outside of the water reserving device. An opening/closing valve is installed in the drainage flow path. A pressure adjusting device adjusts an inner pressure of the water reserving device. A controller controls the opening/closing valve and the pressure adjusting device, such that the controller controls the opening/closing valve from a closed state to an opened state, in a state of decompressing the inner pressure of the water reserving device by the pressure adjusting device when the fuel cell system is stopped.

In another embodiment, the invention provides a method of draining a fuel cell system. The fuel cell system includes a fuel cell for generating electric power by electrochemically reacting a fuel gas with an oxidizer gas, a water reserving device for reserving the generation water resulting from reacting the fuel gas and the oxidizer gas, a drainage flow path for discharging the generation water within the water reserving device from an end opened to an outside of the water reserving device, an opening/closing valve installed in the drainage flow path, a pressure adjusting device for adjusting the inner pressure of the water reserving device, and a controller for controlling the opening/closing valve and the pressure adjusting device. The method includes controlling the opening/closing valve from a closed state to an opened state, and decompressing the inner pressure of the water reserving device by the pressure adjusting device when the fuel cell system is stopped.

According to the present invention, when the system is stopped, the opening/closing valve is controlled from the closed state to the opened state when decompressing the inner pressure of the water reserving device by using the pressure adjusting device. Thus, it is not necessary to discharge the generation water to the outside by actively spilling out the fuel gas in order to remove the water in the opening/closing valve. Therefore, freezing of the opening/closing device can be prevented while preventing the discharge of the extra gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention.

Fig. 1 is a block diagram of a iύel cell system constructed in accordance with an embodiment of the present invention.

Fig. 2 is a constitutional view of a drainage apparatus 15 in accordance with a first embodiment.

Fig. 3 is a flow chart of a freeze preventing process in accordance with an embodiment of the present invention. Fig. 4 is an explanatory view showing a corresponding relationship between a pressure difference between an inner pressure of a separator tank 16 and an opening end pressure (atmospheric pressure) of a downstream drainage flow path L14 and a time required for generation water to move to the separator tank 16 rather than an opening/closing valve 17.

Fig. 5 is a schematic constitutional view of a drainage apparatus 15A in accordance with a second embodiment.

Fig. 6 is a schematic constitutional view of a drainage apparatus 15B in accordance with a third embodiment. Fig. 7 is a schematic constitutional view of a drainage apparatus 15C in accordance with a fourth embodiment.

Fig. 8 is a schematic constitutional view of a drainage apparatus 15D in accordance with a fifth embodiment.

Fig. 9 is a flow chart of a freeze preventing process in accordance with the fifth embodiment.

Fig. 10 is a schematic constitutional view of a drainage apparatus 15E in accordance with a sixth embodiment.

Fig. 11 is a schematic constitutional view of a drainage apparatus 15F in accordance with a seventh embodiment. Fig. 12 is an explanatory view of volume Va of an upstream drainage flow path Ll 3.

Fig. 13 is a flow chart of a freeze preventing process in accordance with the seventh embodiment.

Fig. 14 is a flow chart of a freeze preventing process in accordance with an eighth embodiment. Fig. 15 is a schematic constitutional view of a drainage apparatus 15G in accordance with a ninth embodiment.

Fig. 16 is a schematic constitutional view of a drainage apparatus 15H in accordance with a tenth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Fig. 1 is a block diagram of a fuel cell system constructed in accordance with an embodiment of the present invention. The fuel cell system is a power source of a motor (not shown) for operating a vehicle and is mounted on a vehicle.

The fuel cell system includes a fuel cell stack 1 formed by interposing a fuel cell structure body into a separator and stacking them upon one another. In the fuel cell structure body, an oxidizer electrode and a fuel electrode are facedly installed by interposing a solid polymer electrolytic membrane therebetween. The fuel cell stack 1 is configured such that the fuel gas is supplied to each fuel electrode via a fuel gas flow path (not shown) formed within the stack while the oxidizer gas is supplied to each oxidizer electrode via an oxidizer gas flow path (not shown) formed within the stack. By doing so, the fuel cell stack 1 generates electric power by electrochemically reacting such gases. In the present embodiment, hydrogen is used for a fuel gas and air is used for an oxidizer gas.

The fuel cell system having such a fuel cell stack 1 includes a hydrogen system 10 for supplying hydrogen to the fuel cell stack 1 and an air system 20 for supplying air to the fuel cell stack 1. In the hydrogen system 10, the hydrogen (fuel gas) is supplied from a fuel reserving device for reserving the hydrogen (e.g., a fuel tank 11 such as a high pressure hydrogen tank) through a hydrogen supplying flow path LlO to the fuel cell stack 1. Specifically, a fuel tank root valve (not shown) is installed in a downstream of the fuel tank 11. When the fuel tank root valve is in an opened state, the hydrogen within the fuel tank 11 flows out to the hydrogen supplying flow path LlO. The high pressure hydrogen from the fuel tank 11 is mechanically decompressed to a predetermined pressure by a decompressing valve (not shown) installed further downstream than the fuel tank root valve. The decompressed hydrogen is further decompressed by a hydrogen pressure adjusting valve 12 installed further downstream than the decompressing valve, and then supplied to the fuel cell stack 1. An opening degree of the hydrogen adjusting valve 12 is controlled by a control portion 30 which will be explained below such that the hydrogen pressure supplied to the fuel cell stack 1 becomes a desired value.

Discharging gas (including unused hydrogen) from the fuel electrode of the fuel cell stack 1 is discharged to a hydrogen circulating flow path LI l. The hydrogen circulating flow path Ll 1 is connected at the other end thereof to the hydrogen supplying flow path LlO placed further downstream than the hydrogen pressure adjusting valve 12. A hydrogen circulating device (e.g., a circulating pump 13) is provided in the hydrogen circulating flow path LIl. The discharging gas from the fuel cell stack 1 is circulated to a supplying side of the hydrogen in the fuel cell stack 1 by the hydrogen circulating device. The fuel ratio of the hydrogen can be improved by such a circulating system. A driving amount of the circulating pump 13, that is, its revolution, is controlled by the control portion 30 such that a flow rate of the hydrogen supplied to the fuel cell stack 1 becomes a desired value.

However, in the case of using air as the oxidizer gas, since nitrogen within the air is transmitted from the oxidizer electrode to the fuel electrode, a nitrogen concentration of the gas within the circulating system tends to increase and hydrogen partial pressure tends to decrease. To this end, a hydrogen discharging flow path L 12 for discharging the gas within the hydrogen system is connected to the hydrogen circulating flow path LIl. In the hydrogen discharging flow path L 12, a fuzzy valve 14 is installed. Discharging gas (including nitrogen, unused hydrogen, etc.) flowing via the hydrogen circulating flow path LIl is discharged to the outside by switching an opened/closed state of the fuzzy valve 14. Depending on an operating state of the fuel cell stack 1, the opened/closed state of the fuzzy valve 14 is controlled by the control portion 30. For example, the fuzzy valve 14 is basically controlled in the closed state and estimates the nitrogen concentration within the fuel electrode. Otherwise, the fuzzy valve 14 is switched from the closed state to the opened state in a predetermined period as necessary. To this end, the nitrogen together with the unreacted hydrogen become fuzzy from the hydrogen system 10 to thereby prevent a decrease of the hydrogen partial pressure. The fuel discharging flow path Ll 2 is connected to an air discharging flow path L21 which will be explained below. The discharging gas from the fuzzy valve 14 is diluted by the air discharged from the fuel cell stack 1 and then discharged to the outside.

Further, in the hydrogen circulating flow path LIl, a drainage apparatus 15 for discharging the generation water resulting from the generation of the fuel cell stack 1 is installed upstream from the circulating pump 13. Fig. 2 is a schematic constitutional view of the drainage apparatus 15 in accordance with the first embodiment. The drainage apparatus 15 is mainly constituted of a separator tank 16 and an opening/closing valve 17.

The separator tank 16 has an approximately cylindrical shaped tank including a space within an inner portion thereof as a main body. A division plate 16a having an opening in a center portion thereof is inscribed at a middle portion of the main body. The division plate 16a divides an inner portion of the main body into upper and lower sides. A space in an upper side serves as a gas-liquid separating portion 16b and a space in a lower side serves as a water reserving portion 16c. Mixed fluid of the circulating gas, mainly including the hydrogen and the generation water, is introduced into the gas-liquid separating portion 16b. The introduced mixed fluid swivels along a wall surface in an inner portion of the gas-liquid separating portion 16b to be separated into a gas component (circulating gas) and a liquid component (generation water). The separated circulating gas is flowed out to a downstream side of the hydrogen circulating flow path LIl via an opening formed on a top portion of the main body. Meanwhile, the separated generation water is moved to a lower side of the main body by its own weight and reserved in the water reserving portion 16c.

In the lower portion of the main body, a discharging port 16d is formed. The discharging port 16d is an opening for discharging the generation water reserved in the water reserving portion 16c. An upstream drainage flow path Ll 3 is connected to the discharging port 16d. The upstream drainage flow path Ll 3 is extended to a vertically lower direction and is then curved and extended to a horizontal direction. Further, the upstream drainage flow path L 13 is connected to a downstream drainage flow path L14 via the opening/closing valve 17. In the present embodiment, the downstream drainage flow path L14 is extended to a horizontal direction and is opened to the outside at the end thereof. An opened/closed state of the opening/closing valve 17 is controlled by the control portion 30. Further, an orifice 18 for partially reducing a flow path diameter is installed in the upstream drainage flow path Ll 3. Also, a water repellent treatment is performed on the opening/closing valve 17 and a flow path around the opening/closing valve 17. Further, as used herein, the terms "upstream" and "downstream" are used on the basis of a flow of the generation water discharged from the separator tank 16 to the outside of the system.

Referring back to Fig. 1, in the air system 20, if atmospheric air is received by a compressor 21, the air (oxidizer gas) is pressurized and then supplied to the fuel cell stack 1 via an air supplying flow path L20. A humidifying device 22 is installed at a rear end of the compressor 21 in the air supplying flow path L20 so that the air supplied to the fuel cell stack 1 is humidified as much as the generating performance of the fuel cell stack 1 is not deteriorated. The discharging gas (air wherein the oxygen is consumed) from the fuel cell stack 1 is discharged to the outside (atmosphere) via an air discharging flow path L21. An air pressure adjusting vale 23 is installed in the air discharging flow path L21. An opening degree of the air pressure adjusting valve 23 and a driving amount (revolution) of the compressor 21 are controlled by the control portion 30 such that the air pressure supplied to the fuel cell stack 1 and the air flow rate become the desired values. In such a fuel cell system, a power extracting device (not shown) is connected to the fuel cell stack 1. The power extracting device is controlled by the control portion 30 and extracts a required power (e.g., electric power) from the fuel cell stack 1. The electric power extracted by the power extracting device is supplied to a driving motor (not shown) via a motor control portion (not shown) for controlling a driving motor (not shown) of the vehicle. Further, a rechargeable secondary battery (not shown) is connected to the power extracting device in parallel with the motor control portion. The electric power extracted by the power extracting device and regenerative electric power from the driving motor are charged to the secondary battery. Further, the electric power accumulated to the secondary battery is supplied to the driving motor via the motor control portion.

For the control portion (control device) 30, for example, a microcomputer mainly including a CPU, a ROM, a RAM and an input/output interface may be used. The control portion 30 controls an operating state of the fuel cell stack 1 by controlling each portion of the system. According to a control program stored in the ROM, the control portion 30 performs, for example, an opening degree calculation of the hydrogen pressure adjusting valve 12, an opening degree calculation of the air pressure adjusting valve 23, a revolution calculation of the circulation pump 13 and a revolution calculation of the compressor 21. Further, the control portion 30 outputs a control amount (control signal) calculated from such calculations against various actuators and controls the opening degree of the hydrogen pressure adjusting valve 12, the opening degree of the air pressure adjusting valve 23, the revolution of the circulating pump 13 and the revolution of the compressor 21.

Also, in the present embodiment, the control portion 30 serves to control the drainage apparatus 15 and performs a treatment on the generation water reserved within the separator tank 16 by controlling the opening/closing valve 17 of the drainage apparatus 15. Generally, the control portion 30 controls the state of the opening/closing valve 17 based on a water level of the generation water in the water reserving portion 16c of the separator tank 16. Specifically, when the water level of the generation water is increased in the water reserving portion 16c and arrives at an upper limit water level, which is pre-established to be lower than a full water level of the water reserving portion 16c, the control portion 30 controls the opening/closing valve 17 to be in the opened state, thereby starting a drainage of the generation water. Further, when the water level of the generation water arrives at a lower limit water level (upper limit water level > lower limit water level), the control portion 30 controls the opening/closing valve 17 to be in the closed state, thereby finishing the drainage of the generation water. The upper and lower limit water levels are established by considering a water level change by an inclination or vibration caused by driving of a vehicle (e.g., when mounted on the vehicle). For example, the upper limit water level is established as a water level as much as the generation water is not introduced into the air-liquid separating portion 16b. The lower limit water level is established as a water level of the generation water remaining in a lower portion of the water reserving portion 16c as much as the separated circulating gas is not discharged from the discharging port 16d. Also, when the fuel cell system is stopped, the control portion 30 performs a freeze preventing process for preventing the opening/closing valve 17 from being frozen during the system stop period. Further, details of the freeze preventing process will be explained below. In the control portion 30, signals from various sensors including sensors 31 and 32 are inputted. A water level detecting sensor 31 is a sensor for detecting a water level of the generation water reserved within the water reserving portion 16c. A water detecting sensor 32 is installed in the upstream drainage flow path Ll 3 and detects whether the generation water exists in a region of the sensor. In the fuel cell system having such constitutions, the freeze preventing process performed by the control portion 30 will be explained below. Fig. 3 is a flow chart showing a freeze preventing process in accordance with the present embodiment. The process shown in this flow chart is interrogated when the fuel cell system is stopped and then performed by the control portion 30. Here, a determination on the stopping of the system by the control portion 30 is performed when an ignition switch is turned off by a user or when an idle state of the vehicle is maintained for a predetermined time.

First, in the step 10 (SlO), the opening/closing valve 17 is controlled to be in the opened state.

In the step 11 (SIl), after referring to a detecting value of the water level detecting sensor 31, it is determined whether a water level of the generation water within the water reserving portion 16c is equal to or less than a standard water level. The standard water level is pre-established to be lower than the upper limit water level from the viewpoint that the generation water within the water reserving portion 16c does not exceed the upper limit water level by the generation water within the upstream drainage flow path L 13, which moves into the separator tank 16 resulting from a negative pressure control, as will be explained below. Specifically, the standard water level is established between the lower limit water level and a water level within the water reserving portion 16c when the volumetric integral generation water corresponding to the upstream drainage flow path L13 is subtracted from the generation water within the water reserving portion 16c at the time of the upper limit water level.

If it is determined as positive in SIl, that is, if the present water level of the generation water is equal to or less than the standard water level, then the process proceeds to the step 12 (S 12) so that the opening/closing valve 17 is controlled to be in the closed state. Meanwhile, if it is determined as negative in SIl, that is, if the present water level of the generation water is not equal to or less than the standard water level, then the process in SIl is performed again after a predetermined time. In the step 13 (S 13) after the S 12, the negative pressure control is started. Such a negative pressure control is a control for decompressing a pressure state within the separator tank 16 to be a pressure lower than an outer portion pressure at an opening end side of the downstream drainage flow path L14 (atmospheric pressure in the present embodiment), i.e., to be a negative pressure. As discussed above, an inner space of the separator tank 16 constitutes a part of the hydrogen circulating flow path L 11 , and the hydrogen system 10 including the hydrogen circulating flow path Ll 1 is formed as a closed system. To this end, the pressure within the separator tank 16 can be decompressed by driving the circulating pump 13 installed in the hydrogen circulating flow path LIl or by consuming the hydrogen in the fuel electrode of the fuel cell stack 1 by extracting the power by using the power extracting device when stopping the hydrogen supply from the fuel tank 11. In the step 14 (S 14), it is determined whether the inner pressure of the separator tank 16 is a negative pressure. Such a process can be determined, for example, by directly monitoring the inner pressure by installing a pressure sensor within the separator tank 16. Further, the atmospheric pressure (outer pressure at the opening end side of the downstream drainage flow path L 14), which becomes a comparison standard, may refer to a detecting value obtained by installing the pressure sensor in the outer portion, or may refer to a representative value of the atmospheric pressure prepared beforehand, which becomes a standard.

Also, when the negative pressure control is performed by driving the circulating pump 13, the inner pressure of the separator tank 16 may be indirectly monitored by referring to a supply pressure of the hydrogen right before stopping the system, a revolution of the circulating pump 13 or an elapsed time after starting the negative pressure control. Optionally, when the negative pressure control is performed by consuming the hydrogen by using the power extracting device, the inner pressure of the separator bank 16 may be indirectly monitored by referring to a supply pressure of the hydrogen right before stopping the system, an extracting amount of the power by the power extracting device or an elapsed time after starting the negative pressure control. Further, when using the indirect monitoring method, it is preferred that a relationship between an estimate value of the inner pressure of the separator tank 16 and each parameter is pre-obtained as a map or table via experiments or simulations and based on such map or table, the pressure of the inner space of the separator tank 16 is estimated.

If the process is determined as positive in S14, that is, if the inner pressure of the separator tank 16 is the negative pressure, then the process proceeds to the step 15 (S 15), thereby finishing the negative pressure control. Meanwhile, if the process is determined as negative in S 14, that is, if the inner pressure of the separator tank 16 is not the negative pressure, then the process in S 14 is performed again after a predetermined time.

In the step 16 (S 16), the opening/closing valve 17 is controlled to be the opened state.

In the step 17 (S 17), it is determined whether the generation water around the opening/closing valve 17 in the drainage flow paths Ll 3 and L14 is removed. The inner pressure of the separator tank 16 becomes a negative pressure state by a series of the genitive pressure controls in S13 to S 15. To this end, if the opening/closing valve 17 becomes the opened state in S 16, then the generation water existing within the upstream drainage flow path L 13 is moved to the separator tank side 16 due to a pressure difference between the inner pressure of the separator tank 16 and the outer pressure (atmospheric pressure) at the opening end side of the downstream drainage flow path L 14. Accordingly, since it is determined by the water detecting sensor 32 installed in the upstream side of the opening/closing valve 17 whether the generation water exists, it can be determined whether the generation water within the upstream drainage flow path Ll 3 is moved to the separator tank side 16, that is, whether the generation water around the opening/closing valve 17 is removed.

If the process is determined as positive in S 17, that is, if the generation water is not detected by the water detecting sensor 32, then the process proceeds to the step 18 (S 18), thereby controlling the opening/closing valve 17 to be the closed state. Meanwhile, if the process is determined as negative in S 17, that is, if the generation water is detected by the water detecting sensor 32, then the process in S 14 is performed again after a predetermined time. Further, whether the generation water around the opening/closing valve 17 is removed, is assessed by the water detecting sensor 32 determining whether the generation water exists. However, the present invention is not limited to such a configuration. For example, at the timing of controlling the opening/closing valve 17 to be in the closed state in S 12, a water level of the water reserving portion 16c detected by the water level detecting sensor 31 is stored. Also, an increment of the water level is obtained via experiments or simulations when the generation water corresponding to a volume of the upstream drainage flow path L13 is flowed into the separator tank side 16. Moreover, when the detecting value from the water level detecting sensor 31 is monitored and when the water level of the generation water corresponding to the upstream drainage flow path Ll 3 is increased from the stored water level, the above determination may be performed. Also, as a separate determining method, as shown in Fig. 4, a corresponding relationship is pre-obtained via experiments or simulations between a pressure difference of the inner pressure of the separator tank 16 and the opening end pressure (atmospheric pressure) of the downstream drainage flow path L 14, and a time required for the generation water to move to the separator tank 16 after controlling the opening/closing valve 17 to be the opened state. Also, referring to such a corresponding relationship, based on the pressure difference resulting from the negative pressure control between the inner pressure of the separator tank 16 and the atmospheric pressure, when a time is elapsed required for the generation water within the upstream drainage flow path L13 to move to the separator tank side 16, it may be determined that the generation water around the opening/closing valve 17 is removed. Also, the corresponding relationship between the pressure difference and the time shown in Fig. 4 is indicated as a linear relationship. However, such a relationship may be approximated as a quadratic function relationship or a step relationship.

Further, each determining method discussed above may be performed individually as well as in combination thereof. As such, in the present embodiment, the drainage apparatus for draining water within the fuel cell system having the fuel cell for generating the electric power by electrochemically reacting the fuel gas and the oxidizer gas includes a water reserving device, a drainage flow path, an opening/closing device, a pressure adjusting device and a control device. Here, the water reserving device serves for reserving the generation water resulting from the generation of the fuel cell stack 1 in an inside thereof. In the present embodiment, the water reserving portion 16c of the separator tank 16 corresponds thereto. The drainage flow path serves for discharging the generation water within the separator tank 16 from an end opened to an outer portion of the separator tank 16, and in the present embodiment, the drainage flow paths L13 and L14 correspond thereto. The opening/closing device is installed in the flow paths Ll 3 and Ll 4 and serves for opening/closing the flow paths, and in the present invention, the opening/closing valve 17 corresponds thereto. The pressure adjusting device serves for adjusting the inner pressure of the water reserving device, and in the present embodiment, the circulating pump 13 of the hydrogen system 10 or the power extracting device corresponds thereto. The control device serves for controlling the opening/closing valve 17 and the pressure adjusting device, and in the present embodiment, the control portion 30 corresponds thereto. Here, in the state of decompressing the inner pressure of the separator tank 16 lower than the outer pressure at the opening end side of the downstream drainage flow path L14 by using the pressure adjusting device, when the fuel cell system is stopped, the control portion 30 performs the freeze preventing process for controlling the opening/closing valve 17 to be in the opened state and then to be in the closed state at the same time of controlling the opening/closing valve 17 to be in the opened state.

According to such a constitution, since the generation water within the drainage flow paths L13 and L 14 is moved to the separator tank side 16c due to the pressure difference between the inner pressure of the separator tank 16c and the outer pressure at the opening end side of the downstream drainage flow path L 14, the generation water around the opening/closing valve 17 can be removed. Further, since the opening/closing valve 17 is closed when the inner pressure of the separator tank 16c is the negative pressure, a state can be avoided wherein the opening/closing valve 17 is submerged. Also, since the generation water within the upstream drainage flow path Ll 3 is merely moved to the separator tank side 16c, the discharge of gas within the system to the outside via the drainage flow paths Ll 3 and L14 can be avoided. To this end, the freezing of the opening/closing valve 17 can be prevented while preventing the discharge of the extra gas. Further, the drainage apparatus in accordance with the present embodiment further includes a water level detecting device (a water level detecting sensor 31 in the present embodiment) for detecting the water level of the generation water reserved within the separator tank 16. Here, the control portion 30 controls the opening/closing valve 17 to be in the opened state in the freeze preventing process. Then, based on a detecting result of the water level detecting sensor 31, when the water level of the generation water within the separator tank 16 is increased as much as a volume of the drainage flow path Ll 3 at an upstream side further than the opening/closing valve 17, the control portion 30 controls the opening/closing valve 17 to be the closed state. According to such a constitution, since a water level change of the separator tank 16 can be accurately judged, from an amount of the generation water moved to the separator tank side 16 due to the pressure difference, it can be accurately determined whether the generation water around the opening/closing valve 17 is removed.

Also, the drainage apparatus in accordance with the present embodiment is installed in the drainage flow path Ll 3 upstream from the opening/closing valve 17 and further includes a water detecting device (a water detecting sensor 32 in the present embodiment) for detecting the generation water in the flow path region. Here, the control portion controls the opening/closing valve 17 to be in the opened state in the freeze preventing process. Then, when the generation water is not detected by the water detecting sensor 32, the control portion 30 controls the opening/closing valve 17 to be in the closed state. According to such a constitution, since it can be detected whether the generation water exists in the drainage flow path Ll 3 upstream from the opening/closing valve 17, it can be determined whether the generation water around the opening/closing valve 17 is removed before the generation water within the flow path is completely moved to the separator tank 16. To this end, a time required for the process can be reduced. Also, it can be restrained that impurities from the outside are intermixed into the separator tank 16 or the circulating system.

Further, in the drainage apparatus in accordance with the present embodiment, the control portion 30 controls the opening/closing valve 17 to be in the opened state in the freeze preventing process. Then, when a time pre-established according to the pressure difference of the inner pressure of the separator tank 16 and the pressure at the opening end side of the drainage flow path L14 is elapsed, the control portion 30 controls the opening/closing valve 17 to be in the closed state. From such a method, it can be determined without using a sensor whether the generation water around the opening/closing valve 17 is removed. Further, it can be restrained that impurities from the outside are intermixed into the water reserving device or within the system by appropriately establishing such a time beforehand.

Also, in the drainage apparatus in accordance with the present embodiment, during a general operation of the system, the control portion 30 controls the opening/closing valve 17 to be the closed state. This is to start the discharge of the generation water when the water level of the generation water reaches the upper limit water level established lower than the full water level of the separator tank 16, while the control portion 30 controls the opening/closing valve 17 to be in the closed state. As such, the discharge of the generation water can be completed when the water level of the generation water reaches the lower limit water level established lower than the upper limit water level. According to such a constitution, the generation water reserved in the water reserving portion 16c of the separator tank 16 does not flow into the gas-liquid separating portion 16b, and the gas is not discharged from the discharging port 16d of the water reserving portion 16c to the outside, when the water level is changed by an inclination or shaking caused by operating a vehicle.

Further, in the drainage apparatus according to the present embodiment, for the drainage flow paths Ll 3 and L 14, the volume of the flow path Ll 3 upstream from the opening/closing valve 17 is established smaller than a value of subtracting a volume of the generation water within the separator tank 16 (water reserving portion 16c) at the upper limit water level from a volume of the generation water within the separator tank 16 (water reserving portion 16c) at the full water level. According to such a constitution, it can be restrained by the freeze preventing process that the generation water is overflowed from the water reserving portion 16c when the generation water within the drainage flow path ' Ll 3 is flowed into the separator tank 16.

Also, in the drainage apparatus according to the present embodiment, as a precondition for performing the freeze preventing process, the control portion 30 controls the opening/closing valve 17 to be in the opened state. Then, based on the detecting result by the water level detecting sensor 31, the control portion 30 controls the opening/closing valve 17 to be in the closed state when the generation water within the separator tank 16 is equal to or less than the standard water level. Here, the standard water level is established between the lower limit water level and a water level within the water reserving portion 16c when the volumetric integral generation water corresponding to the upstream drainage flow path Ll 3 upstream from the opening/closing valve 17 is subtracted from the generation water within the water reserving portion 16c at the time of the upper limit water level. According to such a constitution, since the freeze preventing process can be performed after the water level within the separator tank 16 becomes the same condition, the control can be stabilized. Further, whether a water level increased when the generation water is moved from the drainage flow path L13 to the separator tank side 16 can be determined beforehand by performing the process having the standard water level as a standard. Thus, it can be accurately determined whether the generation water around the opening/closing valve 17 is removed. Also, it can be restrained that impurities from the outside are intermixed into the water reserving means or within the system.

Further, the drainage apparatus in accordance with the present embodiment further includes an orifice installed in the drainage flow path Ll 3 upstream from the opening/closing valve 17, reducing the flow path diameter. According to such a constitution, a flow speed of the generation water flowed into the separator tank 16 becomes slower. Thus, a control performance of the opening/closing valve 17 can be improved. Second Embodiment

Fig. 5 is a schematic constitutional view of a drainage apparatus 15A in accordance with a second embodiment. The drainage apparatus 15A in accordance with the second embodiment differs from the drainage apparatus 15 in accordance with the first embodiment in terms of the shape of the drainage flow path. Further, the members having the same function as in the first embodiment are denoted by the same reference numerals and explanations thereof will be omitted herein. Also, since the details of the freeze restraining process are the same as in the first embodiment, explanations thereof will be omitted herein.

The drainage apparatus 15A in accordance with the second embodiment mainly includes the separator tank 16 and the opening/closing valve 17. In the lower portion of the main body of the separator tank 16, the discharging port 16d is formed. The discharging port 16d is an opening for discharging the generation water reserved in the water reserving portion 16c. An upstream drainage flow path Ll 5 is connected to the discharging port 16d. The upstream drainage flow path Ll 5 is extended to a vertically lower direction and then curved to a horizontal direction. It is curved again and extended to a vertically lower direction. The upstream drainage flow path Ll 5 is connected to the downstream drainage flow path L14 via the opening/closing valve 17. An orifice (not shown) for partially reducing a flow path diameter is installed in the upstream drainage flow path Ll 5. Further, in the present embodiment, the downstream drainage flow path L 14 has a shape extended to a lower direction and an end thereof is opened to the atmosphere. An opened/closed state of the opening/closing valve 17 is controlled by the control portion 30. Also, the water repellent process is performed on the opening/closing valve 17 and a flow path around the opening/closing valve 17.

As such, in the present embodiment, the drainage flow paths L15 and L 14 have shapes wherein a side downstream of the opening/closing valve 17 is extended to a lower direction. As explained in the first embodiment, since the inner portion of the separator tank 16 is established as a negative pressure in the freeze preventing process, air is suctioned from the downstream drainage flow path L14 resulting therefrom. In a case wherein the generation water is remained in the downstream flow path L 14, there is a problem that the generation water within the flow path is suctioned with the suctioned air and then stopped around the opening/closing valve 17. In this regard, it is preferred that in the freeze preventing process, the generation water does not exist within the downstream drainage flow path L 14. To this end, in the present embodiment, it is configured that since the downstream drainage flow path L14 is extended to a lower direction, the generation water within the downstream drainage flow path L14 is discharged to the outside of the system by its own weight. By doing so, the freezing preventing of the opening/closing valve 17 can be effectively performed. Third Embodiment

Fig. 6 is a schematic constitutional view of a drainage apparatus 15B in accordance with a third embodiment. The drainage apparatus 15B in accordance with the third embodiment differs from the drainage apparatus 15 in accordance with the first embodiment in terms of the shape of the drainage flow path. Further, the members having the same function as in the first embodiment are denoted by the same reference numerals and explanations thereof will be omitted herein. Also, since the details of the freeze preventing process are the same as in the first embodiment, explanations thereof will be omitted herein. The drainage apparatus 15B in accordance with the third embodiment mainly includes the separator tank 16 and the opening/closing valve 17. An upstream drainage flow path Ll 6 is installed in the inner portion of the separator tank 16. The upstream drainage flow path Ll 6 is extended to a vertically upper direction from the lower portion of the water reserving portion 16c, curved to a horizontal direction of the gas-liquid separating portion 16b, and then extended to the outer portion of the separator tank 16. It is thus connected to the downstream drainage flow path L14 via the opening/closing valve 17. Further, in the present embodiment, the downstream drainage flow path L14 is extended to a horizontal direction and its end is opened to the atmosphere. An opened/closed state of the opening/closing valve 17 is controlled by the control portion 30. Also, the water repellent process is performed on the opening/closing valve 17 and a flow path around the opening/closing valve 17. As such, in the present embodiment, the opening/closing valve 17 of the drainage apparatus 15B is arranged in a vertically upper direction than a liquid surface of the generation water within the separator tank 16 when the system is stopped. To this end, in the course of stopping the fuel cell system, although the inner pressure of the separator tank 16 is increased to become close to the atmospheric pressure, it can be restrained that the generation water within the upstream drainage flow path Ll 6 arrives at the opening/closing valve 17. In this regard, it can be restrained that the opening/closing valve 17 is submerged. Further, according to such a constitution, since water condensed in the hydrogen circulating flow path LIl of the hydrogen system 10 is reserved in the separator tank 16, the water is restrained from being flowed into the drainage flow path L 16. To this end, freezing of the opening/closing valve 17 can be more effectively prevented. Fourth Embodiment

Fig. 7 is a schematic constitutional view of a drainage apparatus 15C in accordance with a fourth embodiment. The drainage apparatus 15C in accordance with the fourth embodiment differs from the drainage apparatus 15 in accordance with the first embodiment in terms of the shape of the drainage flow path. Further, the members having the same function as in the first embodiment are denoted by the same reference numerals and explanations thereof will be omitted herein. Also, since the details of the freeze preventing process are the same as in the first embodiment, explanations thereof will be omitted herein.

The drainage apparatus 15C in accordance with the fourth embodiment mainly includes the separator tank 16 and the opening/closing valve 17. An upstream drainage flow path L16 is installed in the inner portion of the separator tank 16. The upstream drainage flow path L16 is extended to a vertically upper direction from the lower portion of the water reserving portion 16c. It is then curved and extended to the outer portion of the separator tank 16, thereby being connected to the downstream drainage flow path L14 via the opening/closing valve 17. An orifice (not shown) for partially reducing a flow path diameter is installed in the upstream drainage flow path Ll 6. Further, in the present embodiment, the downstream drainage flow path L14 is extended to a lower direction and its end is opened to the atmosphere. An opened/closed state of the opening/closing valve 17 is controlled by the control portion 30. Also, the water repellent process is performed on the opening/closing valve 17 and a flow path around the opening/closing valve 17. As such, in the present embodiment, the opening/closing valve 17 of the drainage apparatus is arranged in a vertically upper direction than the liquid surface of the generation water within the separator tank 16 when the system is stopped. Further, the drainage flow paths L16 and L14 are established in a shape wherein a downstream side thereof is further downstream than the opening/closing valve 17 is a lower direction. According to such a constitution, the functions and effects of the second and third embodiments can be obtained, respectively. To this end, the freeze of the opening/closing valve 17 can be more effectively restrained. Fifth Embodiment

Fig. 8 is a schematic constitutional view of a drainage apparatus 15D in accordance with a fifth embodiment. The fifth embodiment differs from the first embodiment in terms of the drainage apparatus and the freeze preventing process. Further, such differences will be explained below, but explanations of the same constitutions are omitted herein. The upstream drainage flow path Ll 3 of the drainage apparatus 15D in accordance with the fifth embodiment is extended to a vertically lower direction. It is then curved and extended to a horizontal direction, and then curved and extended to a vertically upper direction. Further, the upstream drainage flow path Ll 3 is extended to a direction above the liquid surface of the generation water within the separator tank 16, i.e., a position corresponding to the gas-liquid separating portion 16b. The upstream drainage flow path Ll 3 is curved and extended to a horizontal direction. The upstream drainage flow path Ll 3 is connected to the downstream drainage flow path L14 via the opening/closing valve 17 installed in its opening end. The downstream drainage flow path L 14 is extended to a horizontal direction. Thus, its end is opened to the outside. Also, the opening/closing valve 17 is arranged in a position having a height corresponding to the gas-liquid separating portion 16b. Further, the water repellent process is performed on the opening/closing valve 17 and the drainage flow paths Ll 3 and L 14.

In the fuel cell system having such a constitution, the freeze preventing process performed by the control portion 30 will be explained below. Fig. 9 is a flow chart showing the order of the freeze preventing process in accordance with the present embodiment. The process shown in this flow chart is interrogated when the fuel cell system is stopped and then the process is performed by the control portion 30. Here, a determination on the stopping of the system by the control portion 30 is performed when an ignition switch is turned off by a user or when an idle state of the vehicle is maintained for a predetermined time.

First, in SlO, the atmospheric pressure control is performed. Since the hydrogen is supplied to the fuel cell stack 1 while the fuel cell system is operated, the hydrogen circulating flow path LIl including the inner space of the separator tank 16 becomes a positive pressure state. Such an atmospheric pressure control is a control to decompress the pressure state within the separator tank 16 to the outer pressure (atmospheric pressure in the present embodiment) at the opening end side of the downstream drainage flow paths L13 and L 14. As discussed above, the inner space of the separator tank 16 constitutes a part of the hydrogen circulating flow path LIl, and the hydrogen system 10 including the hydrogen circulating flow path LIl is formed as a closed system. In the present embodiment, since the hydrogen circulating flow path LIl is decompressed to the atmospheric pressure by controlling the fuzzy valve 14 to be in the opened state when stopping the hydrogen supply from the fuel tank 11, the inner pressure of the separator tank 16 is decompressed to the atmospheric pressure.

In SIl, the opening/closing valve 17 is controlled to be in the opened state. Then, the present routine is finished. As such, in the present embodiment, the drainage flow path has an upper direction shape wherein a part of the flow path is extended to an upper direction. The drainage flow path serves for guiding the generation water within the separator tank 16 to a direction above the liquid surface of the generation water and discharging it from an end opened to the outside, and the drainage flow path L 13 corresponds thereto. Further, the opening/closing device is installed in the flow path Ll 3 and serves for opening/closing the flow path, and the opening/closing valve 17 corresponds thereto. Also, the pressure adjusting device serves for adjusting the inner pressure of the separator tank 16, and the fuzzy valve 14 corresponds thereto. Further, the control device serves for controlling the opening/closing valve 17 and the fuzzy valve 14, and in the present embodiment, the control portion 30 corresponds thereto in the present embodiment.

In such a case, the control portion 30 performs the freeze preventing process for decompressing the inner pressure of the separator tank 16 by the fuzzy valve 14 having the outer pressure at the opening end side of the drainage flow path L13 as a target value when the fuel cell system is stopped, and then controlling the opening/closing valve 17 to be in the opened state. Here, when performing the freeze preventing process, the opening/closing valve 17 is arranged in a direction above the liquid surface of the generation water within the drainage flow path. Here, references B to E in Fig. 8 indicate the moving states of the generation water by the freeze preventing process. Since the hydrogen is supplied to the fuel cell stack 1 while the fuel cell system is operated, when the freeze preventing process resulting from the stopping of the system is started, the hydrogen circulating flow path LIl including the inner space of the separator tank 16 becomes the positive pressure state. Further, since the opening/closing valve 17 becomes the closed state, the generation water becomes a predetermined water level A within the separator tank 16 when filling up an entire area of the upstream drainage flow path L 13.

In the case of performing the freeze preventing process, the upstream drainage flow path Ll 3 is opened to the atmosphere via the downstream drainage flow path L 14. As such, the pressures exerted on the liquid surface within the separator tank 16 and the liquid surface within the upstream drainage flow path Ll 3 correspond to each other. Here, the opening/closing valve 17 is arranged in a direction above the liquid surface A within the separator tank 16. In this regard, the generation water within the upstream drainage flow path Ll 3 is moved to the separator tank side 16 by its own weight. To this end, in the upstream drainage flow path L 13, the liquid surface is dropped to a direction lower than the opening/closing valve 17. In the separator tank 16, the liquid surface is increased from the liquid surface A as much as the moving amount of the generation water. Further, the liquid surface in the separator tank 16 (liquid surface B) and the liquid surface in the upstream drainage flow path L13 (liquid surface C) are in an equilibrium state with each other when the liquid surface B and the liquid surface C are on the same horizontal surface.

As such, according to the present embodiment, since the inner pressure of the separator tank 16 is decompressed to be the atmospheric pressure and then the opening/closing valve 17 is controlled to be in the opened state as the freeze preventing process, the liquid surface within the upstream drainage flow path L13 is decreased.

Therefore, it can be restrained that the opening/closing valve 17 is immersed within the generation water while the system is stopped. Further, in order to remove the water in the opening/closing valve 17, it is not necessary to discharge the generation water to the outside by actively spilling the hydrogen into the separator tank 16. Therefore, the freezing of the opening/closing device can be prevented while preventing the discharge of the extra gas. Further, in the present embodiment, the inner pressure of the separator tank 16 is decompressed to be the atmospheric pressure by controlling the fuzzy valve 14 to be in the opened state. However, the present invention is not limited to such a configuration. For example, without opening the fuzzy valve 14, the pressure within the separator tank 16 may be decompressed to the atmospheric pressure by consuming the hydrogen within the hydrogen circulating system. In such a case, the inner pressure of the separator tank 16 may be indirectly monitored by referring to a supply pressure of the hydrogen right before stopping the system, an extracting amount of the power by the power extracting device or an elapsed time after extracting the power. Further, in such a case, it is preferred that a relationship between an estimate value of the inner pressure of the separator tank 16 and each parameter is previously obtained as a map or table, and the pressure of the inner space of the separator bank 16 is estimated based on such map or table. Also, a target value of the inner pressure of the separator tank 16, i.e., the atmospheric pressure may be referred to by obtaining the atmospheric pressure itself by the sensor or by preparing a representative value of the atmospheric pressure by considering the use environment. Also, in the present embodiment, the pressure within the separator tank 16 is decompressed to the atmospheric pressure. By doing so, since the liquid surface of the upstream drainage flow path Ll 3 is decreased, the liquid surface B within the separator tank 16 and the liquid surface C within the upstream flow path L13 reach an equilibrium state in the same horizontal surface. Also, based on the liquid surface C within the upstream drainage flow path L13, a layout of the opening/closing valve 17 is prescribed. However, it is not strictly demanded that the pressure within the separator tank 16 is decompressed to the atmospheric pressure (outer pressure at the opening end side of the drainage flow paths Ll 3 and L 14). That is, although the inner pressure of the separator tank 16 is not completely decompressed to the atmospheric pressure, if the decompressing control is performed to become close to the atmospheric pressure, then the liquid surface of the upstream drainage flow path L13 is decreased as shown in Fig. 8. In this regard, although a liquid surface D within the separator tank 16 and a liquid surface E within the upstream drainage flow path Ll 3 do not correspond to each other in the same horizontal surface, both liquid surfaces reach an equilibrium state. In such a case, since the opening/closing valve 17 is arranged in a direction above the liquid surface of the generation water within the drainage flow paths Ll 3 and L14 after the opening/closing valve 17 is controlled to be in the opened state by the freeze preventing process, it can be preventing that the opening/closing valve 17 is immersed within the generation water while the system is stopped. To this end, the freezing of the opening/closing valve 17 can be prevented. Sixth Embodiment Fig. 10 is a schematic constitutional view of a drainage apparatus 15E in accordance with a sixth embodiment. The drainage apparatus 15E in accordance with the sixth embodiment differs from the fifth embodiment in terms of the shape of the drainage flow path. Further, such differences will be explained below, but explanations of the same constitutions are omitted herein. The drainage apparatus 15E in accordance with the sixth embodiment mainly includes the separator tank 16 and the opening/closing valve 17. In the present embodiment, a part of the upstream drainage flow path Ll 5 is installed in the inner portion of the separator tank 16 and extended to a vertically upper direction from the lower portion of the water reserving portion 16c. Thus, the part of the upstream drainage flow path Ll 5 is curved to a direction above the liquid surface of the generation water within the separator tank 16 (specifically to a horizontal direction of the gas-liquid separating portion 16b). Thereafter, the upstream drainage flow path Ll 5 is extended to the outer portion of the separator tank 16 and then connected to the downstream drainage flow path L14 via the opening/closing valve 17. The downstream drainage flow path L14 is extended to the horizontal direction and opened to the atmosphere at the end thereof.

As such, according to the drainage apparatus 15E in accordance with the present embodiment, since the opening/closing valve 17 is controlled to be in the opened state by the freeze preventing process, the liquid surface within the upstream drainage flow path Ll 5 is decreased so that it can obtain the same effects as in the second embodiment. Further, since a part of the upstream drainage flow path Ll 5 is arranged in the inner portion of the separator tank 16, a size of the apparatus can be reduced. Therefore, the mountability to the vehicle can be improved. Seventh Embodiment

Fig. 11 is a schematic constitutional view of a drainage apparatus 15F in accordance with a seventh embodiment. The drainage apparatus 15F in accordance with the seventh embodiment differs from the fifth embodiment in terms of performing the control by determining an upper limit value (upper limit water level) and a lower limit value (lower limit water level) of the water level within the separator tank 16 (specifically the water reserving portion 16c). Further, such differences will be explained below, but the explanations of the same constitution are omitted herein.

In the seventh embodiment, during a general operation of the fuel cell system, the control portion 30 controls a state of the opening/closing valve 17 based on the water level of the generation water within the water reserving portion 16c of the separator tank 16. Specifically, when the water level of the generation water is increased in the water reserving portion 16c and reaches the upper limit water level pre-established to be lower than the foil water level of the water reserving portion 16c, the control portion 30 controls the opening/closing valve 17 to be in the opened state, thereby starting the drainage of the generation water. Further, when the water level of the generation water reaches the lower limit water level (upper limit water level > lower limit water level), the control portion 30 controls the opening/closing valve 17 to be in the closed state, thereby finishing the drainage of the generation water. To this end, the generation water within the separator tank 16 is within a range between the upper limit water level and the lower limit water level. The upper limit water level and the lower limit water level are established by considering a water level change by an inclination or vibration caused by driving a vehicle (e.g., when mounted on the vehicle). For example, the upper limit water level is established as a water level as much as the generation water is not introduced into the air- liquid separating portion 16b. The lower limit water level is established as a water level of the generation water remaining in a lower portion of the water reserving portion 16c as much as the separated circulating gas is not discharged from the discharging port 16d.

Further, water level detecting sensors 33 and 34 are installed in the water reserving portion 16c of the separator tank 16. The upper limit water level detecting sensor 33 is a sensor for detecting the upper limit water level within the water reserving portion 16c. The lower limit water level detecting sensor 34 is a sensor for detecting the lower limit water level within the water reserving portion 16c. Detecting results from each water level detecting sensor 33 and 34 are outputted to the control portion 30.

Also, in the present embodiment, as shown in Fig. 12, a volume Va of the upstream drainage flow path L13 is established to be lower than a value (volume Vb) of subtracting a volume of the generation water within the separator tank 16 (water reserving portion 16c) at the upper limit water level from a volume of the generation water within the separator tank 16 (water reserving portion 16c) at the full water level.

Fig. 13 is a flow chart showing the order of the freeze preventing process in accordance with the seventh embodiment. The process shown in Fig. 13 is interrogated when the fuel cell system is stopped and then performed by the control portion 30. First, in the step 20 (S20), the opening/closing valve 17 is controlled to be in the opened state. As discussed above, when the freeze preventing process resulting from the stop of the system is started, the hydrogen circulating flow path LI l including the inner space of the separator tank 16 becomes the positive pressure state. To this end, in S20, since the opening/closing valve 17 is controlled to be in the opened state, the generation water within the separator tank 16 is pushed out by the inner pressure. This is so that the generation water is discharged to the outside via the drainage flow paths Ll 3 and L 14. In the step 21 (S21), it is determined whether the generation water within the separator tank 16 arrives at a standard water level. In the present embodiment, for the standard water level, a lower limit water level is established for performing a drainage control of the generation water within the separator tank 16. To this end, referring to the detecting result of the lower limit water level detecting sensor 34, the control portion 30 determines whether the water level of the generation water arrives at the lower limit water level.

If it is determined as positive in S21, that is, if the water level of the generation water reaches the lower limit water level, then the process proceeds to a step 22 (S22). Meanwhile, if it is determined as negative in S21, that is, if the water level of the generation water does not arrive at the lower limit water level, then the process in S21 is performed after a predetermined time.

In S22, the opening/closing valve 17 is controlled to be in the closed state. Also, in the step 23 (S23), the atmospheric pressure control is performed as in SlO of the first embodiment. In the step 24 (S24), the opening/closing valve 17 is controlled to be in the opened state as in SIl of the first embodiment.

As such, according to the present embodiment, it can obtain the same effects as in the fifth embodiment. Further, since the liquid surface of the generation water within the separator tank 16 is decreased to the standard water level (lower limit water level in the present embodiment) prior to the atmospheric pressure control, the amount of the generation water moved from the drainage flow path Ll 3 to the separator tank side 16 is increased. In this regard, since a decrease range of the liquid surface in the drainage flow path Ll 3 becomes larger, it can be preventing that the opening/closing valve 17 is immerged into the generation water. To this end, the freezing of the opening/closing valve 17 can be more effectively prevented. Eighth Embodiment

Fig. 14 is a flow chart showing the order of the freeze preventing process in accordance with an eighth embodiment. The freeze restraining process in accordance with the eighth embodiment will be explained below. Further, the differences from the fifth embodiment will be explained below, but the explanations of the same constitution are omitted herein.

First, in the step 30 (S30), the atmospheric pressure control is performed as in SlO of the fifth embodiment. In the step 31 (S31), the opening/closing valve 17 is controlled to be in the opened state as in SIl of the fifth embodiment.

In the step 32 (S32), it is determined whether removal of the generation water in the opening/closing valve 17 is completed. In the present embodiment, it is determined whether the generation water around the opening/closing valve 17 is removed by a time elapsed after controlling the opening/closing valve 17 to be in the opened state. Thus, a time required to remove the generation water from the opening/closing valve 17 is obtained as a standard time via experiments or simulations based on the atmospheric pressure control and the open control of the opening/closing valve 17. Further, assessment is performed by comparing the standard time and the elapsed time. If it is determined as positive in S32, that is, if a time after controlling the opening/closing valve 17 to be in the opened state arrives at the standard time, then the process proceeds to the step 33 (S33). Meanwhile, if it is determined as negative in S32, that is, a time after controlling the opening/closing valve 17 to be in the closed state does not arrive at the standard time, then the process in S32 is performed again after a predetermined time.

Also, in S33, the opening/closing valve 17 is controlled to be in the closed state. Then, the present routine is finished. As such, according to the present embodiment, after the opening/closing valve 17 is controlled to be in the opened state, the opening/closing valve 17 is finally controlled to be in the closed state. To this end, it can be restrained that impurities from the outside are intermixed into the separator tank 16 via the drainage flow paths L13 and L 14. Ninth Embodiment

Fig. 15 is a schematic constitutional view of a drainage apparatus 15G in accordance with a ninth embodiment. The drainage apparatus 15G in accordance with the ninth embodiment differs from the fifth embodiment in view of installing the water level detecting sensor in the upstream drainage flow path Ll 3. Further, the differences from the fifth embodiment will be explained below, but the explanations of the same constitution are omitted herein.

Specifically, the water level detecting sensor 32 is installed in the upstream drainage flow path L13. Detecting results from the water level detecting sensor 32 are outputted against the control portion 30. Further, the water level detecting sensor 32 is arranged in a direction above the liquid surface of the generation water within the drainage flow path Ll 3 after the opening/closing valve 17 is controlled to be in the opened state by the freeze preventing process.

Further, in the present embodiment, the orifice 18 for reducing the flow path diameter is installed in a position of the upstream drainage flow path L 13, which is contacted to the opening/closing valve 17.

In the drainage apparatus 15G having such a constitution, the control portion 30 performs the atmospheric pressure control and then controls the opening/closing valve 17 to be in the opened state. Also, referring to the detecting result of the water level detecting sensor 32, the control portion 30 controls the opening/closing valve 17 to be in the closed state on the condition that the liquid surface of the upstream drainage flow path Ll 3 is decreased so that the liquid surface arrives at a position of the sensor.

As such, according to the present embodiment, since the opening/closing valve 17 is finally controlled to be in the closed state, the intermixture of impurities can be restrained. Further, the opening/closing valve 17 can be closed in a step wherein the liquid surface is decreased to a position of the water level detecting sensor 32 installed in the lower portion of the opening/closing valve 17, that is, before the liquid surfaces of the separator tank 16 and the upstream drainage flow path L 13 reach the equilibrium state. Therefore, the processing time can be reduced.

Further, since the orifice 18 is installed in contact with the opening/closing valve 17, when the opening/closing valve 17 is controlled to be in the opened state, the orifice 18 is not submerged by the generation water. Therefore, since a time of the generation water to move to the separator tank 16 is reduced, the processing time can be further reduced. Tenth Embodiment

Fig. 16 is a schematic constitutional view of a drainage apparatus 15H in accordance with a tenth embodiment. The drainage apparatus 15H in accordance with the tenth embodiment differs from the fifth embodiment in terms of the shape of the drainage flow path. Further, the differences from the fifth embodiment will be explained below, but the explanations of the same constitution are omitted herein.

The drainage apparatus 15H in accordance with the tenth embodiment mainly includes the separator tank 16 and the opening/closing valve 17. In the lower portion of the main body of the separator tank 16, the discharging port 16d is formed. The discharging port 16d is an opening for discharging the generation water reserved in the water reserving portion 16c. The upstream drainage flow path Ll 6 is connected to the discharging port 16d. The upstream drainage flow path Ll 6 is connected to a downstream drainage flow path Ll 7 via the opening/closing valve 17. Thus, the generation water within the water reserving portion 16c is discharged to the outside via the upstream drainage flow path L16 and the downstream drainage flow path Ll 7 by the hydrogen circulating system, that is, by the inner pressure of the separator tank 16 on a condition that the opening/closing valve 17 is in the opened state. In the present embodiment, the upstream drainage flow path Ll 6 is extended to a vertically lower direction and then curved and extended to a horizontal direction, and then curved and extended to a vertically upper direction. Further, if the upstream drainage flow path Ll 6 is extended to a direction above the generation water within the separator tank 16, that is, to a position corresponding to the gas/liquid separation portion 16b in the present embodiment, the upstream drainage flow path Ll 6 is curved and extended to a horizontal direction. Thereafter, the upstream drainage flow path L16 is extended to a vertically lower direction and connected to the downstream drainage flow path Ll 7 via the opening/closing valve 17 installed in the opening end of the upstream drainage flow path L 16. In the present embodiment, the downstream drainage flow path Ll 7 is extended to a lower direction and its end is opened to the atmosphere. The opened/closed state of the opening/closing valve 17 is controlled by the control portion 30.

As such, in the present embodiment, the upstream drainage flow path Ll 6 has a curved shape wherein a part of the flow path is upwardly extended while downwardly extended via a curved portion. Further, the upstream drainage flow path Ll 6 guides the generation water within the separator tank 16 to a direction above the liquid surface of the generation water. It then discharges the generation water from the end opened to the outside. According to such a constitution, the same functions and effects as the fifth embodiment can be obtained. The downstream drainage flow path Ll 7 is oriented to a lower direction so that the generation water around the opening/closing valve 17 is discharged to the outside of the system by its own weight. To this end, the freezing preventing of the opening/closing valve 17 can be effectively performed.

Further, in each embodiment discussed above, a configuration of applying the drainage apparatus 15 to the hydrogen system 10 is explained. However, the present invention is not limited to such a configuration but may apply the drainage apparatus 15 to the air system 10. Also, the drainage apparatus in each embodiment may include a combination described in the above embodiments as well as a combination of other various features without deviating from the subject matter or scope of the present invention.

While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and equivalents thereof. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.

Claims

CLAIMS:

1. A drainage apparatus for draining water within a fuel cell system, the fuel cell system having a fuel cell for generating electric power by electrochemically reacting a fuel gas with an oxidizer gas, the drainage apparatus comprising: a water reserving device that reserves a generation water resulting from reacting the fuel gas with the oxidizer gas; a drainage flow path that discharges the generation water within the water reserving device from an end opened to an outside of the water reserving device; an opening/closing valve installed in the drainage flow path; a pressure adjusting device that adjusts an inner pressure of the water reserving device; and a controller that controls the opening/closing valve and the pressure adjusting device, wherein the controller controls the opening/closing valve from a closed state to an opened state, in a state of decompressing the inner pressure of the water reserving device by the pressure adjusting device when the fuel cell system is stopped.

2. The drainage apparatus of Claim 1, wherein the controller controls the opening/closing valve to an opened state and then to a closed state.

3. The drainage apparatus of Claim 2, wherein the controller decompresses the inner pressure to be lower than an outer pressure at an opening end side of the drainage flow path.

4. The drainage apparatus of Claim 2, further comprising a water level detecting sensor for detecting a water level of the generation water reserved within the water reserving device, wherein the controller controls the opening/closing valve to be in the closed state if the generation water within the water reserving device reaches a pre-established standard water level based on a detecting result of the water detecting sensor.

5. The drainage apparatus of Claim 4, wherein the standard water level is set to be a water level when a water level of the generation water within the water reserving device is increased by as much as a volume of the drainage flow path from the water reserving device to the opening/closing valve.

6. The drainage apparatus of Claim 2, further comprising a water detecting sensor installed in the drainage flow path closer to the water reserving device than to the opening/closing valve, and detects the generation water around the water detecting sensor, wherein the controller controls the opening/closing valve to be in the closed state when the generation water is not detected by the water detecting device after controlling the opening valve to be in the opened state.

7. The drainage apparatus of Claim 2, wherein the controller controls the opening/closing valve to be in the closed state when a pre-established time is elapsed depending on a pressure difference between a decompressed inner pressure of the water reserving device and a pressure at the opening end side of the drainage flow path after controlling the opening/closing valve to be in the opened state.

8. The drainage apparatus of Claim 2, further comprising a water level detecting device for detecting a water level of the generation water reserved within the water reserving device, wherein during a generation operation of the system, the controller starts a drainage of the generation water by controlling the opening/closing valve to be in the opened state when the water level of the generation water reaches an upper limit water level established lower than a full water level of the water reserving device, and the controller finishes the drainage of the generation water by controlling the opening/closing valve to be in the closed state when the water level of the generation water reaches a lower limit water level established lower than the upper limit water level.

9. The drainage apparatus of Claim 8, wherein a volume of the drainage flow path from the water reserving device to the opening/closing valve is set to be lower than a value determined by subtracting a volume of the generation water within the water reserving device at the upper limit water level from a volume of the generation water within the water reserving device at the full water level.

10. The drainage apparatus of Claim 8, wherein the lower limit water level is a water level of the inner portion of the water reserving device when the volume of the generation water corresponding to the drainage flow path from the water reserving device to the opening/closing valve is subtracted from the generation water within the water reserving portion at the upper limit water level.

11. The drainage apparatus of Claim 1, wherein the opening/closing valve is arranged above a liquid surface of the generation water within the water reserving device when the system is stopped.

12. The drainage apparatus of Claim 1, wherein the drainage flow path has an upper direction shape in which a part of the flow path is extended to an upper direction, and wherein the drainage flow path guides the generation water within the water reserving device to a direction above the liquid surface of the generation water and then discharges the generation water from the end opened to the outside.

13. The drainage apparatus of Claim 12, wherein the controller decompresses the inner pressure of the water reserving device by controlling the opening/closing valve to be in the opened state such that the liquid surface of the generation water within the drainage flow path is at the same level as the liquid surface of the generation water within the water reserving device.

14. The drainage apparatus of Claim 11, wherein the drainage flow path has a curved shape in which a part of the flow path is extended to an upper direction while extended to a lower direction through a curved portion, and wherein the opening/closing valve is installed in the opening end side rather than the curved portion of the drainage flow path.

15. The drainage apparatus of Claim 4, comprising a water level detecting sensor at the drainage flow path, wherein the controller controls the opening/closing valve from the opened state to the closed state on the condition that the liquid surface within the drainage flow path is decreased to a second standard water level detected by the water level detecting sensor.

16. The drainage apparatus of Claim 1, further comprising an orifice installed in the drainage flow path nearer the water reserving device than the opening/closing valve, reducing a flow path diameter.

17. The drainage apparatus of Claim 1, further comprising an orifice installed in the drainage flow path in a position in contact with the opening/closing valve.

18. The drainage apparatus of Claim 1, wherein the drainage flow path has a shape in which the end side is extended to a lower direction than the opening/closing valve.

19. The drainage apparatus of Claim 1, wherein the controller decompresses the inner pressure to a target value of the outer pressure at the opening end side of the drainage flow path.

20. A method of draining a fuel cell system, the fuel cell system including a fuel cell for generating electric power by electrochemically reacting a fuel gas with an oxidizer gas, a water reserving device for reserving the generation water resulting from reacting the fuel gas and the oxidizer gas, a drainage flow path for discharging the generation water within the water reserving device from an end opened to an outside of the water reserving device, an opening/closing valve installed in the drainage flow path, a pressure adjusting device for adjusting the inner pressure of the water reserving device, and a controller for controlling the opening/closing valve and the pressure adjusting device, the method comprising: controlling the opening/closing valve from a closed state to an opened state, and decompressing the inner pressure of the water reserving device by the pressure adjusting device when the fuel cell system is stopped.