JP4821126B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a structure of a stack case that houses a fuel cell stack.

  2. Description of the Related Art A fuel cell stack that generates power using hydrogen as a fuel is known as a power source for driving a moving body such as an electric vehicle. The fuel cell stack is configured by stacking a plurality of cells and fastening them from both sides with bolts or the like. Due to such a configuration, when an impact from a road surface or an impact due to a collision is applied to the fuel cell stack, the fastening force for fastening the cell is momentarily reduced below the pressure inside the fuel cell stack. There is a possibility that the internal liquid, that is, the refrigerant liquid flowing in the refrigerant liquid flow path or the generated water accumulated in the reaction gas flow path will leak out of the fuel cell stack.

  Usually, the fuel cell stack is mounted on the moving body while being housed in a stack case. Since the stack case is sealed to keep the inside warm and prevent intrusion of water and mud from the outside, the liquid leaked from the fuel cell stack is accumulated in the stack case. However, when a highly conductive liquid accumulates in the stack case, the insulation resistance at the high voltage portion of the fuel cell stack is lowered, and there is a risk of short circuit or leakage.

In order to prevent the above problems from occurring, it is effective to collect the liquid in the fuel cell stack. For example, Patent Document 1 discloses a technique for collecting liquid by inclining the bottom surface of a stack case. Patent Document 1 also discloses a technique in which a water-repellent sheet is laid on the bottom surface of the stack case, wind is sent by a fan, and liquid is collected on the leeward side of the fan.
JP 2002-164070 A Japanese Patent Laid-Open No. 7-282834

  However, when the bottom surface of the stack case is inclined as in the above prior art, the capacity in the case is unnecessarily increased, resulting in an increase in the size of the stack case. In addition, when liquid is collected by the wind power of the fan, it is necessary to provide an extra space in the stack case for installing the fan. In this case as well, the outer shape of the stack case is increased. From the viewpoint of ease of mounting on a moving body such as a vehicle, the outer shape of the stack case should be as small as possible.

  The present invention has been made to solve the above-described problems, and provides a fuel cell capable of reliably collecting the liquid generated in the stack case without causing an increase in the size of the stack case. With the goal.

In order to achieve the above object, a first invention provides a fuel cell comprising a fuel cell stack and a stack case that houses the fuel cell stack.
The bottom surface of the stack case is provided with a groove for collecting the liquid generated in the stack case.

  According to a second invention, in the first invention, a part of the groove is provided with a liquid reservoir portion having a groove depth deeper than that of the other part.

  A third invention is characterized in that, in the second invention, a detecting means for detecting the liquid in the liquid reservoir is provided.

  A fourth invention is characterized in that, in the third invention, the detection means is provided outside the stack case.

  A fifth invention is characterized in that, in any one of the first to fourth inventions, the groove is constituted by an uneven shape formed on a bottom plate of the stack case.

  According to the first aspect, the liquid generated in the stack case can be collected by the groove provided on the bottom surface of the stack case. For this reason, the enlargement of a stack case external shape like the case where the bottom face of a stack case is inclined is not caused.

  Further, according to the second invention, the liquid generated in the stack case can be collected in the liquid reservoir. According to the third aspect, by detecting the liquid collected in the liquid reservoir, it is possible to reliably detect the generation of liquid in the stack case, such as liquid leakage from the fuel cell stack. According to the fourth invention, it is possible to prevent failure and deterioration of the detection means by arranging the detection means outside the stack case in a high temperature and high humidity atmosphere.

  According to the fifth invention, the unevenness formed on the bottom plate of the stack case can increase the rigidity of the stack case, and can prevent the fuel cell stack disposed in the stack case from being twisted or the like. it can. In addition, since the uneven shape can be easily formed by press molding or the like, a groove can be easily provided on the bottom surface of the stack case.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a side sectional view showing a configuration of a fuel cell as an embodiment of the present invention. In this embodiment, the fuel cell of the present invention is configured as a power source for driving an electric vehicle. In this fuel cell, the stack case for storing the fuel cell stack 40 is composed of two pieces: a hat-type upper case 10 and a plate-type lower case 20. A fuel cell stack 40 is disposed on the lower case 20 so that the cell stacking direction is horizontal, and the upper case 10 is covered so as to cover the fuel cell stack 40 from above. Both the upper case 10 and the lower case 20 are coated at least on the inner surface with an insulating material (for example, polyethylene). A gasket 50 is interposed between the flange of the upper case 10 and the edge of the lower case 20 to prevent water and mud from entering the stack case. The hat shape of the upper case 10 can be formed by press deep drawing such as aluminum.

  The fuel cell stack 40 is disposed on the lower case 20 via an insulator mount 60. End plates 44 are attached to both ends of the fuel cell stack 40 in the cell stacking direction. The insulator mount 60 is sandwiched between the end plate 44 and the upper surface of the lower case 20. A plurality of pipes 46 are connected to the end plate 44 of the fuel cell stack 40 for supplying and discharging refrigerant liquid and reaction gas. The pipe 46 extends through the lower case 20 to the outside of the stack case. A portion of the lower case 20 through which the pipe 46 passes is sealed with a gasket or the like.

  The lower case 20 is attached to a vehicle frame (or subframe) (not shown) via a body member 30. The body member 30 also serves as a reinforcing member for reinforcing the rigidity of the lower case 20. The body member 30 and the vehicle frame are welded, and the lower case 20 and the body member 30 are fastened with bolts 34. The bolt 34 extends through the insulator mount 60 to the end plate 44 of the fuel cell stack 40, and fastens the end plate 44 and the insulator mount 60 to the lower case 20.

  The upper case 10 and the lower case 20 are fastened by a detachable fastener such as a bolt. When inspecting the fuel cell stack 40 or replacing parts, the upper case 10 can be removed from the lower case 20 to expose both ends and the upper surface of the fuel cell stack 40. The pipe 46 and the like are connected to the end of the fuel cell stack 40 as described above, and the cell monitor 42 indicating the power generation status of the cell is mounted on the upper surface. By exposing these maintenance parts, it becomes possible to perform inspection work and parts replacement work with the fuel cell stack 40 mounted on the vehicle.

  FIG. 2 is a top view of the fuel cell with the upper case 10 removed, and FIG. 3 is a top view of the fuel cell with the fuel cell stack 40 further removed, that is, a top view of the lower case 20. is there. In FIG. 3, a through hole through which the pipe 46 passes is omitted. On the upper surface of the lower case 20, as shown in FIG. 3, a plurality of rows of grooves 22 are formed vertically and horizontally in a lattice shape. FIG. 4 is a cross-sectional view taken along the line XX of FIG. 3. As shown in FIG. 4, ribs 26 are formed along the grooves 22 on the lower surface of the lower case 20. By forming the ribs 26, the thickness of the lower case 20 can be made substantially constant, stress concentration in the groove 22 can be relaxed, and the bending strength of the lower case 20 can be improved. Further, a concave portion (a liquid reservoir portion) 24 that is circular and deeper than the groove 22 is formed in the center portion of the lower case 20, and several grooves 22 in vertical and horizontal directions communicate with the concave portion 24. . In addition, the groove | channel 22, the rib 26, and the recessed part 24 can be shape | molded by the casting containing aluminum and magnesium die-casting, the press molding of a metal plate material, etc.

  In a fuel cell mounted on an electric vehicle, the cell fastening force of the fuel cell stack 40 is momentarily relaxed by an input such as an impact from the road surface, and the generated water in the reaction gas flow path or the refrigerant liquid in the refrigerant liquid flow path It may leak out. In addition, during operation of the fuel cell stack 40, the temperature inside the stack case becomes high, so that condensation may occur on the inner surface of the stack case. Liquid leaking from the fuel cell stack 40 and water condensed on the inner surface of the stack case are dropped on the lower case 20 which is the bottom surface and collected by the grooves 22 formed on the upper surface of the lower case 20. The liquid collected in the groove 22 moves in the groove 22 due to vibration during traveling of the vehicle and G in the plane direction, and eventually flows into the central recess 24. The recess 24 is formed with a discharge hole 24a at the center thereof. A drain container 70 disposed immediately below the lower case 20 is connected to the discharge hole 24a. At the bottom of the drain container 70, there is provided a check valve 72 that allows liquid to be discharged from the inside of the stack case while preventing water and mud from entering from the outside of the stack case. The liquid that has flowed into the recess 24 accumulates in the drain container 70 and is discharged from the check valve 72 as droplets to the outside of the stack case.

  Further, the drain container 70 is provided with a liquid level detector 74 and a resistance measuring device 76. The liquid level detector 74 is a sensor that outputs a signal when the liquid level of the liquid accumulated in the drain container 70 reaches a predetermined level. The maximum flow rate of the droplets discharged from the check valve 72 is set to a value larger than the amount of condensed water generated in the stack case. Therefore, when there is no abnormality in the fuel cell stack 40, the liquid level in the drain container 70 does not rise to the detection height of the liquid level detector 74. However, when the generated water leaks from the reaction gas flow path of the fuel cell stack 40 or the refrigerant liquid leaks from the refrigerant liquid flow path, the inflow amount of the liquid flowing into the drain container 70 is the discharge amount. The liquid level rises to the detection height of the liquid level detector 74. Accordingly, by detecting the liquid level with the liquid level detector 74, it is possible to detect the leakage of the liquid from the fuel cell stack 40.

  The resistance measuring device 76 is a sensor that measures the electrical resistance value of the liquid accumulated in the drain container 70. The resistance value varies depending on the composition of the liquid. For example, there is a difference in resistance value between the case where the liquid is only water and the case where the refrigerant liquid is included. In general, the refrigerant liquid contains ethylene glycol as a main component, but ethylene glycol has high insulating properties, and its resistance value is extremely large compared to that of water. Therefore, by measuring the resistance value of the liquid in the drain container 70 by the resistance measuring device 76, it can be determined whether or not the liquid contains the refrigerant liquid.

  Both the liquid level detector 74 and the resistance measuring device 76 are connected to an ECU (Electronic Control Unit) 80. The ECU 80 determines liquid leakage from the fuel cell stack 40 based on information transmitted from the liquid level detector 74 and the resistance measuring device 76, respectively. The flowchart of FIG. 5 shows a routine executed by the ECU 80 to determine liquid leakage.

  In the first step 100 of the routine shown in FIG. 5, it is determined whether or not the liquid level is detected by the liquid level detector 74, that is, whether or not the liquid level has reached the detection level of the liquid level detector 74. Is done. When no detection signal is output from the liquid level detector 74, it can be determined that there is no liquid leakage from the fuel cell stack 40. Conversely, when the liquid level is detected by the liquid level detector 74, it can be determined that some liquid has leaked from the fuel cell stack 40. In the next step 102 in this case, it is determined whether or not the resistance value measured by the resistance measuring device 76 is equal to or greater than a predetermined reference value. The reference value is set to a value larger than the water resistance value.

  As a result of the determination in step 102, when the measured resistance value is smaller than the reference value, it is possible to determine that the liquid leaking from the fuel cell stack 40 is generated water in the reaction gas flow path. In this case, the ECU 80 outputs a warning signal for notifying the driver that the generated water has leaked (step 104). On the other hand, when the measured resistance value is greater than or equal to the reference value, it can be determined that the liquid leaking from the fuel cell stack 40 is the refrigerant liquid flowing through the refrigerant liquid flow path. In this case, the ECU 80 outputs a warning signal for notifying the driver that the refrigerant liquid has leaked (step 106). The warning signal is input to a warning device (not shown) in the passenger compartment, and the warning device notifies the driver of the abnormality by lighting a lamp or sound.

  As described above, the fuel cell according to this embodiment has the following characteristics. The first feature is that a groove 22 is formed in the lower case 20 which is the bottom surface of the stack case, and condensed water or the like is collected by the groove 22. According to this, the outer shape of the stack case is not unnecessarily enlarged as compared with the case where the case bottom is inclined as in the prior art. According to the fuel cell for a moving body according to the present embodiment, the mountability of the fuel cell to the vehicle can be improved by downsizing the stack case. Further, the condensed water collected in the groove 22 is discharged out of the stack case through the discharge hole 24a, so that the collected condensed water does not overflow into the stack case.

  The second feature is that the leakage of the liquid from the fuel cell stack 40 can be detected separately from the condensed water, and it can be determined whether the leaked liquid is generated water or refrigerant liquid. According to this, it is possible to accurately detect a failure of the fuel cell stack 40, and it is possible to accurately take measures according to the content of the failure.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above embodiment, the grooves 22 formed in the lower case 20 are formed in a lattice shape. However, the shape of the grooves is not limited as long as condensed water dripping on the lower case 20 can be collected. For example, as shown in FIG. 6, a plurality of annular grooves 92a may be formed concentrically, and a recess 94 deeper than the groove 92a may be formed at the center. A discharge hole 94 a is formed in the recess 94. A radial communication groove 92b is provided between the inner and outer annular grooves 92a and between the recess 94 and the annular groove 92a. A buffer portion 92c for preventing backflow is formed at the connecting portion between the communication groove 92b and the outer annular groove 92a. According to this, the condensed water collected in each annular groove 92a gradually moves to the inner annular groove 92a due to vibration during vehicle travel and G in the plane direction, and eventually flows into the central recess 94. It has become.

  Moreover, in the said embodiment, although the liquid level detector 74 and the resistance measuring device 76 are provided as a sensor which detects the leak of the liquid from the fuel cell stack 40, if only the leak of produced water is detected, it will be moisture. A detector or a humidity sensor may be used. As the moisture detector, for example, a detector that inserts a pair of electrodes into an object having a water-containing function such as one obtained by solidifying large saw dust and that is determined by a voltage value of a weak current flowing between the electrodes can be used. When there is moisture near the moisture detector, the moisture density inside changes by absorbing the moisture. If the moisture density changes, the resistance value between the electrodes changes, so the voltage value also changes, thereby detecting the presence and amount of moisture. As the humidity sensor, an electronic resistance change type or capacitance change type used in general home appliances such as a refrigerator and a microwave oven can be used.

  In the above embodiment, the present invention is applied to a fuel cell of an electric vehicle. However, the present invention can be applied not only to a fuel cell for a moving body but also to a stationary fuel cell.

It is side surface sectional drawing which shows the structure of the fuel cell as embodiment of this invention. FIG. 2 is a top view of the fuel cell of FIG. 1 with an upper case removed. FIG. 2 is a top view of the fuel cell of FIG. 1 with an upper case and a fuel cell stack removed. It is XX sectional drawing of FIG. 3 which shows the cross-sectional shape of a lower case. It is a flowchart which shows the routine for determining the leakage of the liquid from a fuel cell stack. It is a figure which shows the modification of the groove shape formed in a lower case.

Explanation of symbols

10 Upper Case 20 Lower Case 22 Groove 24 Recess 24a Discharge Hole 26 Rib 30 Body Member 34 Bolt 40 Fuel Cell Stack 42 Cell Monitor 44 End Plate 46 Pipe 50 Gasket 60 Insulator Mount 70 Drain Container 72 Check Valve 74 Liquid Level Detector 76 Resistance Measuring Instrument 80 ECU

Claims (1)

In a fuel cell for a moving body comprising a fuel cell stack and a stack case for storing the fuel cell stack,
Grooves for collecting the liquid generated in the stack case are formed in a plurality of rows and columns on the upper surface of the bottom plate of the stack case, and ribs are formed along the grooves on the lower surface of the bottom plate of the stack case. A fuel cell characterized by comprising:

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