Drain valve system

Abstract

To provide a technology that can efficiently discharge water stored in a gas-liquid separator.SOLUTION: A drain valve system includes a gas-liquid separator that stores water discharged from a fuel cell, a drain valve that discharges water stored in the gas-liquid separator to the outside, and a control unit that controls opening and closing of the drain valve, and the control unit intermittently opens and closes the drain valve, and decreases the ratio of a valve opening time to a valve closing time of the drain valve as time passes from the start of the opening / closing control.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed herein relates to a drain valve system. [Background technology]

[0002] Patent Document 1 discloses a system that includes a gas-liquid separator that stores water discharged from a fuel cell and a drain valve that discharges the water stored in the gas-liquid separator to the outside. In the system of Patent Document 1, the drain valve may be opened and closed intermittently. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2006-331674 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Patent Document 1, the amount of water stored in the gas-liquid separator decreases over time due to the intermittent opening and closing of the drain valve. In this case, simply opening and closing the drain valve intermittently is inefficient. Therefore, there is room for improvement in the control of the opening and closing of the drain valve. This specification provides a technology that can efficiently discharge water stored in the gas-liquid separator. [Means for solving the problem]

[0005] In a first aspect of the present technology, a drain valve system includes a gas-liquid separator that stores water discharged from a fuel cell, a drain valve for discharging the water stored in the gas-liquid separator to the outside, and a control unit that controls the opening and closing of the drain valve, and the control unit intermittently opens and closes the drain valve, and reduces the ratio of the open time of the drain valve to the closed time as time passes from the start of the opening and closing control.

[0006] In the open / close control that intermittently opens and closes the drain valve, the amount of stored water decreases as time passes from the start of the open / close control as the water stored in the gas-liquid separator is discharged. With the above configuration, the proportion of the open time of the drain valve decreases as the amount of stored water decreases, so the open time is not unnecessarily long and the water stored in the gas-liquid separator can be efficiently discharged.

[0007] In a second aspect, the control unit may shorten the opening time of the drain valve and lengthen the closing time of the drain valve as time passes from the start of the opening / closing control.

[0008] This configuration makes it possible to reduce the ratio of the time the drain valve is open to the time it is closed, and to increase the ratio of the time the valve is closed to the time it is open.This ensures that there is enough time for water to accumulate in the gas-liquid separator, allowing a large amount of water to be discharged at one time, resulting in efficient water discharge. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a fuel cell system equipped with a drain valve system according to an embodiment; [Figure 2] 4 is a timing chart of the opening and closing control in the embodiment. [Figure 3] 10 is a timing chart of opening and closing control according to a modified example. [Figure 4] 10 is a timing chart of opening and closing control according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] A drain valve system 2 of the embodiment will be described with reference to the drawings. Fig. 1 is a schematic diagram of a fuel cell system 4 equipped with the drain valve system 2 of the embodiment. As shown in Fig. 1, the fuel cell system 4 includes a hydrogen tank 12, a fuel cell 10, a gas-liquid separator 14, and a control unit 50. The fuel cell system 4 is mounted on a vehicle (not shown), such as a fuel cell automobile.

[0011] The hydrogen tank 12 stores hydrogen gas (fuel gas) to be supplied to the fuel cell 10. A hydrogen supply passage 30 is connected to the hydrogen tank 12. The upstream end of the hydrogen supply passage 30 is connected to the hydrogen tank 12, and the downstream end is connected to the fuel cell 10. The hydrogen supply passage 30 supplies hydrogen gas from the hydrogen tank 12 to the fuel cell 10.

[0012] The hydrogen supply passage 30 is provided with a solenoid valve 22 and an ejector 16. The solenoid valve 22 opens and closes the hydrogen supply passage 30. When the solenoid valve 22 opens, hydrogen gas is supplied to the fuel cell 10 through the hydrogen supply passage 30. The opening degree of the solenoid valve 22 is adjustable.

[0013] The ejector 16 is provided in the hydrogen supply passage 30 downstream (on the fuel cell 10 side) of the solenoid valve 22. The downstream end of a return passage 36, which will be described later, is connected to the ejector 16. The ejector 16 is a device that uses the pressure of the hydrogen gas flowing through the hydrogen supply passage 30 to suck in gas flowing through the return passage 36 and discharges it to the downstream side of the hydrogen supply passage 30.

[0014] The fuel cell 10 will now be described. In addition to the hydrogen supply passage 30, an air supply passage 32 is connected to the fuel cell 10. The upstream end of the air supply passage 32 is connected to an air supply source (not shown), and the downstream end is connected to the fuel cell 10. Air is supplied from the air supply source to the fuel cell 10 through the air supply passage 32. The upstream end of the air supply passage 32 may be open to the outside air. A pump 18 is provided in the air supply passage 32 to pump air toward the fuel cell 10.

[0015] The fuel cell 10 generates electricity using hydrogen supplied through the hydrogen supply passage 30 and oxygen contained in air supplied through the air supply passage 32. The fuel cell 10 includes, for example, a plurality of battery cells (not shown) stacked inside a container, and each battery cell generates electricity through a chemical reaction between hydrogen and oxygen. The battery cells are, for example, but not limited to, solid oxide fuel cells (SOFCs) or polymer electrolyte fuel cells (PEFCs). When the fuel cell 10 generates electricity, water is produced by the chemical reaction between hydrogen and oxygen. Furthermore, when the fuel cell 10 generates electricity, unreacted hydrogen gas is discharged as off-gas.

[0016] The upstream end of a hydrogen off-gas passage 34 is connected to the fuel cell 10. The downstream end of the hydrogen off-gas passage 34 is connected to the gas-liquid separator 14. The hydrogen off-gas passage 34 discharges water generated in the fuel cell 10 to the gas-liquid separator 14. The hydrogen off-gas passage 34 also discharges off-gas (hydrogen gas) discharged from the fuel cell 10 to the gas-liquid separator 14.

[0017] The fuel cell 10 is further connected to the upstream end of an air off-gas passage 38. The downstream end of the air off-gas passage 38 is connected to an air discharge destination (not shown). The air off-gas passage 38 discharges the air discharged from the fuel cell 10 to the discharge destination.

[0018] The gas-liquid separator 14 will now be described. The gas-liquid separator 14 stores water discharged through the hydrogen off-gas passage 34. In addition to the hydrogen off-gas passage 34, an exhaust water drainage passage 40 and a reflux passage 36 are connected to the gas-liquid separator 14. The hydrogen off-gas passage 34 and the reflux passage 36 are connected to the top of the gas-liquid separator 14, and the exhaust water drainage passage 40 is connected to the bottom of the gas-liquid separator 14.

[0019] The exhaust drain passage 40 is a passage for discharging water stored in the gas-liquid separator 14 to the outside. The downstream end of the exhaust drain passage 40 is connected to a water discharge destination (not shown). Water is discharged from the gas-liquid separator 14 to the discharge destination through the exhaust drain passage 40. The exhaust drain passage 40 is provided with an exhaust drain valve 20 (an example of a drain valve) that opens and closes the exhaust drain passage 40. The exhaust drain valve 20 is composed of, for example, an electromagnetic valve. When the exhaust drain valve 20 opens, water is discharged through the exhaust drain passage 40.

[0020] The upstream end of the return passage 36 is connected to the gas-liquid separator 14, and the downstream end is connected to the hydrogen supply passage 30 via the ejector 16. Due to the pressure of the hydrogen gas flowing through the hydrogen supply passage 30, the off-gas (hydrogen gas) flowing through the return passage 36 is sucked into the hydrogen supply passage 30 via the ejector 16. As a result, the off-gas is supplied from the gas-liquid separator 14 to the hydrogen supply passage 30 via the return passage 36. This off-gas is supplied to the fuel cell 10 via the hydrogen supply passage 30. Therefore, the off-gas (hydrogen gas) discharged from the fuel cell 10 is returned and supplied again to the fuel cell 10. In a modified example, a pump for pressure-feeding the off-gas may be provided to the return passage 36.

[0021] The control unit 50 of the fuel cell system 4 includes, for example, a CPU, a ROM, and a RAM, and executes various controls and processes related to the fuel cell system 4 according to a predetermined program. The control unit 50 is, for example, an ECU (Engine Control Unit) of a vehicle.

[0022] Next, the opening and closing control of the exhaust drain valve 20 will be described. In the above fuel cell system 4 (and the drain valve system 2), the control unit 50 controls the opening and closing of the exhaust drain valve 20. The control unit 50 starts the opening and closing control of the exhaust drain valve 20, for example, when the amount of water stored in the gas-liquid separator 14 exceeds a predetermined upper threshold. The amount of water stored in the gas-liquid separator 14 is detected, for example, by a sensor (not shown) attached to the gas-liquid separator 14. In a modified example, the amount of water stored in the gas-liquid separator 14 may be calculated based on the amount of power generated by the fuel cell 10.

[0023] 2, the control unit 50 intermittently opens and closes the exhaust drainage valve 20 in the opening and closing control of the exhaust drainage valve 20. When intermittently opening and closing the exhaust drainage valve 20, the control unit 50 decreases the ratio of the open time to the closed time of the exhaust drainage valve 20 as more time passes from the start of the opening and closing control. More specifically, the control unit 50 shortens the open time and lengthens the closed time of the exhaust drainage valve 20 as more time passes from the start of the opening and closing control.

[0024] The opening / closing control shown in Figure 2 comprises multiple valve-opening steps S1, S2, ... and multiple valve-closing steps T1, T2, .... Of the multiple valve-opening steps S1, S2, ..., the first valve-opening step S1 has the longest duration, and the last valve-opening step Sx has the shortest duration. The duration of each valve-opening step S2, S3, ... after S2 is shorter than the duration of the previous fully-open valve step. The duration of a certain valve-opening step (e.g., S3) is shorter than the duration of the previous valve-opening step (e.g., S2).

[0025] Furthermore, among the multiple valve closing steps T1, T2, ..., the duration of the first valve closing step T1 is the shortest, and the duration of the last valve closing step Tx is the longest. The duration of each valve closing step T1, T2, ... after T2 is longer than the duration of the previous full valve closing step. The duration of a certain valve closing step (e.g., T3) is longer than the duration of the previous valve closing step (e.g., T2).

[0026] After starting the opening / closing control of the exhaust / drainage valve 20, the control unit 50 ends the opening / closing control of the exhaust / drainage valve 20 when, for example, the amount of water stored in the gas-liquid separator 14 falls below a predetermined lower limit threshold.

[0027] (effect) The above has described the fuel cell system 4 and the drain valve system 2 of the embodiment. As is clear from the above description, the drain valve system 2 of the embodiment includes a gas-liquid separator 14 that stores water discharged from the fuel cell 10, and an exhaust / drain valve 20 that discharges the water stored in the gas-liquid separator 14 to the outside. The control unit 50 intermittently opens and closes the exhaust / drain valve 20, and decreases the ratio of the open valve time to the closed valve time of the exhaust / drain valve 20 as time passes from the start of opening / closing control.

[0028] In a configuration in which the exhaust / drain valve 20 opens and closes intermittently, the amount of stored water decreases as time passes from the start of opening / closing control due to the discharge of water stored in the gas-liquid separator 14. According to the above configuration, the proportion of the open time of the exhaust / drain valve 20 decreases as the amount of stored water decreases, so the open time is not unnecessarily long and the water stored in the gas-liquid separator 14 can be efficiently discharged.

[0029] In the above configuration, the control unit 50 shortens the open time of the exhaust / drain valve 20 and lengthens the closed time as time passes from the start of opening / closing control. With this configuration, the ratio of the open time to the closed time of the exhaust / drain valve 20 can be made smaller. Also, the ratio of the closed time to the open time can be made larger. This ensures time for water to accumulate in the gas-liquid separator 14, allowing a large amount of water to be discharged at one time, thereby enabling efficient discharge of water. Furthermore, by lengthening the closed time of the exhaust / drain valve 20, the amount of hydrogen leaking through the exhaust / drain valve is reduced, improving fuel efficiency.

[0030] (Variation) (1) As shown in FIG. 3, the control unit 50 may shorten the open time of the exhaust / drain valve 20 as time passes from the start of the opening / closing control, and may maintain a constant closed time. In the opening / closing control shown in FIG. 3, the duration of the multiple closing steps T1, T2, ... is the same. The rest is the same as in the above embodiment. Even with this configuration, the ratio of the open time to the closed time of the exhaust / drain valve 20 can be reduced as time passes from the start of the opening / closing control. Therefore, water accumulated in the gas-liquid separator 14 can be efficiently discharged.

[0031] (2) As shown in FIG. 4, the control unit 50 may lengthen the closing time of the exhaust / drain valve 20 as time passes from the start of the opening / closing control, and may maintain a constant opening time. In the opening / closing control shown in FIG. 4, the duration of the multiple valve opening steps S1, S2, ... is the same length. The rest is the same as in the above embodiment. Even with this configuration, the ratio of the opening time of the exhaust / drain valve 20 to the closing time can be made smaller as time passes from the start of the opening / closing control. Therefore, water accumulated in the gas-liquid separator 14 can be efficiently discharged. Furthermore, by lengthening the closing time of the exhaust / drain valve 20, the amount of hydrogen leakage through the exhaust / drain valve is reduced, improving fuel efficiency.

[0032] (3) The exhaust / drain valve 20 may be provided at the connection between the gas / liquid separator 14 and the exhaust / drain passage 40 and may be integral with the gas / liquid separator 14 .

[0033] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0034] 2: Drain valve system, 4: Fuel cell system, 10: Fuel cell, 12: Hydrogen tank, 14: Gas-liquid separator, 16: Ejector, 18: Pump, 20: Exhaust drain valve, 22: Solenoid valve, 30: Hydrogen supply passage, 32: Air supply passage, 34: Hydrogen off-gas passage, 36: Circulation passage, 38: Air off-gas passage, 40: Exhaust drain passage, 50: Control unit

Claims

1. a gas-liquid separator that stores water discharged from the fuel cell; a drain valve for discharging water stored in the gas-liquid separator to the outside; a control unit that controls opening and closing of the drain valve, The control unit intermittently opens and closes the drain valve, and as time passes from the start of opening and closing control, the control unit shortens the open time of the drain valve and lengthens the closed time, thereby reducing the ratio of the open time to the closed time of the drain valve.

2. A gas-liquid separator that stores water discharged from a fuel cell; a drain valve for discharging water stored in the gas-liquid separator to the outside; a control unit that controls opening and closing of the drain valve, The control unit intermittently opens and closes the drain valve, shortening the open time of the drain valve as time passes from the start of opening and closing control, and maintaining a constant closed time, thereby reducing the ratio of the open time to the closed time of the drain valve.

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