JP6637870B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  Hydrogen and air are supplied to a fuel cell stack of a fuel cell system mounted on a vehicle such as an industrial vehicle, and power is generated by causing a chemical reaction between hydrogen and oxygen in the air. Here, when air enters the fuel cell stack while the fuel cell system stops operating and the vehicle is stored, the cells of the fuel cell stack may be oxidized and performance may be reduced.

  Therefore, in Patent Document 1, the hydrogen held between the two closed valves on the hydrogen supply flow path is supplied to the bypass flow path so that the performance of the fuel cell stack is not deteriorated even when the operation of the fuel cell system is stopped. Is supplied to the fuel cell stack via Then, the supplied hydrogen reacts with oxygen in the fuel cell stack to consume oxygen, thereby preventing oxidation of the cell. An orifice is provided in the bypass flow path as flow rate limiting means for limiting the flow rate of hydrogen supplied to the fuel cell stack to a small amount.

JP 2010-086939 A

  However, the flow rate restricting means of the fuel cell system disclosed in Patent Document 1 cannot appropriately adjust the amount of hydrogen flowing into the fuel cell stack from the bypass passage according to the hydrogen concentration of the fuel cell stack 1 at that time. Therefore, it has been difficult to supply an appropriate amount of hydrogen to the fuel cell stack.

  On the other hand, there is a method in which an electromagnetic valve is provided in the bypass flow path, and the control unit controls the electromagnetic valve while monitoring the hydrogen concentration in the hydrogen supply flow path via a sensor to adjust the flow rate of hydrogen in the bypass flow path. . However, adopting such a method of providing an electromagnetic valve complicates the structure of the fuel cell system and increases the manufacturing cost.

  The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide a fuel cell system having a simple structure and capable of appropriately preventing performance degradation of a fuel cell stack when power generation is stopped.

In order to solve the above problems, a fuel cell system according to the present invention includes a fuel cell stack that generates power by reacting hydrogen and oxygen in air, a hydrogen tank that supplies hydrogen to the fuel cell stack, and a fuel tank. A hydrogen supply passage provided between the cell stack and the hydrogen tank and through which hydrogen flows, a pressure adjustment device provided in the hydrogen supply passage to adjust the pressure of hydrogen flowing into the fuel cell stack, and a pressure adjustment device A bypass flow path connected to the hydrogen supply flow path, a relief valve provided in the bypass flow path, and a shut-off valve provided in the bypass flow path. Is higher than a predetermined pressure between the pressure of hydrogen upstream of the relief valve and the pressure of hydrogen downstream of the relief valve. When there is, the relief valve is Ri Do opened, shut-off valve, during the power generation of the fuel cell stack are closed, during the power generation stop of the fuel cell stack is in the open state.

Further, the pressure adjusting device may be an injector .

  ADVANTAGE OF THE INVENTION According to the fuel cell system which concerns on this invention, the performance fall at the time of a power generation stop of a fuel cell stack can be prevented appropriately with a simple structure.

FIG. 1 is a schematic diagram showing a fuel cell system according to an embodiment of the present invention. It is a graph showing a change in the downstream of the hydrogen pressure P _M and upstream of the hydrogen pressure P _L of the relief valve of the bypass flow passage in the fuel cell system shown in FIG. FIG. 6 is a schematic diagram showing a fuel cell system according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, a fuel cell system 100 includes a fuel cell stack 1, an air compressor 2 for supplying air to a cathode side of the fuel cell stack 1, and a hydrogen tank for supplying hydrogen to an anode side of the fuel cell stack 1. 3 is provided. The hydrogen pressure inside the hydrogen tank 3 is, for example, 1 to 35 MPa. Between the air compressor 2 and the fuel cell stack 1, an air supply flow path L1 through which air flows is provided. Further, between the hydrogen tank 3 and the fuel cell stack 1, a hydrogen supply flow path L2 for flowing hydrogen is provided.

  An air cutoff valve 16 is provided in the air supply passage L1. Here, when the air cutoff valve 16 is open, the air compressed by the air compressor 2 flows through the air supply passage L1 and is supplied to the fuel cell stack 1, and when the air cutoff valve 16 is closed, The supply of air to the fuel cell stack 1 stops.

In the hydrogen supply flow path L2, a hydrogen shutoff valve 12, a pressure reducing valve 13, and an injector 4 are sequentially provided from the upstream side to the downstream side. Here, when the hydrogen shutoff valve 12 is in the open state, the high-pressure hydrogen stored in the hydrogen tank 3 is supplied to the fuel cell stack 1 through the hydrogen supply flow path L2, and the hydrogen shutoff valve 12 is in the closed state. At this time, the supply of hydrogen to the fuel cell stack 1 is stopped. The pressure reducing valve 13 reduces the pressure of high-pressure hydrogen flowing from the hydrogen tank 3. The injector 4 is an electromagnetically driven on-off valve that can adjust the flow rate and pressure of hydrogen flowing into the fuel cell stack 1 through the hydrogen supply flow path L2.
Here, the injector 4 constitutes a pressure adjusting device.

  A bypass flow path L3 that bypasses the injector 4 is connected to the hydrogen supply flow path L2. One end of the bypass flow path L3 on the upstream side is connected to a first branch point 4a downstream of the pressure reducing valve 13 and upstream of the injector 4. The other end on the downstream side of the bypass flow path L3 is connected to a second branch point 4b provided downstream of the injector 4. A relief valve 11 is provided in the bypass passage L3.

Here, the downstream and the hydrogen pressure in the upstream portion of the relief valve 11 of the portion upstream of the injector 4 and the bypass flow path L3 of the pressure reducing valve 13 of the hydrogen supply flow path L2 and the first hydrogen pressure P _M. The first hydrogen pressure P _M, is detected by the pressure sensor 7a. Further, the downstream and downstream of the hydrogen pressure in the bypass flow path L3 of the relief valve 11 of the injector 4 of the hydrogen supply flow path L2, i.e. the anode side of the inlet of the hydrogen pressure of the fuel cell stack 1 and the second hydrogen pressure P _L. Second hydrogen pressure P _L is detected by the pressure sensor 7b. Those Specifically, the first hydrogen pressure _{P M} is about 0.85 MPa, while the second hydrogen pressure _{P L} is assumed to take a value of 0.11～0.3MPa, which are not necessarily limited to this value is not. Note that the lower limit pressure of the second hydrogen pressure P _L is P _LL .

  On the exhaust side of the fuel cell stack 1, an air exhaust passage L4 is connected to the cathode side, and a hydrogen exhaust passage L5 is connected to the anode side. The air exhaust passage L4 and the hydrogen exhaust passage L5 are each connected to the diluter 5 on the downstream side. The air exhaust passage L4 is provided with an air pressure regulating valve 14 for adjusting the supply pressure of air. Further, a hydrogen exhaust valve 15 for adjusting the flow rate of the discharged hydrogen is provided in the hydrogen exhaust passage L5.

  Further, a third branch point 6a is provided upstream of the hydrogen exhaust valve 15 in the hydrogen exhaust channel L5, and one end of the hydrogen circulation channel L6 is connected to the third branch point 6a. Further, the other end of the hydrogen circulation flow path L6 is connected to a fourth branch point 6b provided downstream of the second branch point 4b of the hydrogen supply flow path L2. A hydrogen circulation pump 6 is provided in the hydrogen circulation channel L6.

Next, the operation of the fuel cell system 100 will be described with reference to FIGS.
First, when the fuel cell system 100 is operating and the fuel cell stack 1 is generating power, the injector 4, the hydrogen shutoff valve 12, the pressure reducing valve 13, the air pressure regulating valve 14, the hydrogen exhaust valve 15, and the air shutoff valve 16 Is open. Then, compressed air is supplied from the air compressor 2 to the cathode side of the fuel cell stack 1 via the air supply passage L1. The high-pressure hydrogen inside the hydrogen tank 3 flows through the hydrogen supply flow path L2, and the pressure is adjusted by the pressure reducing valve 13 and the injector 4 to be sent to the anode side of the fuel cell stack 1. In the fuel cell stack 1, hydrogen and oxygen in the air cause a chemical reaction to generate electric power and generate water.

  Then, the exhaust gas on the cathode side and the anode side of the fuel cell stack 1 flows out to the air exhaust passage L4 and the hydrogen exhaust passage L5, respectively. Air containing unreacted oxygen flows through the air exhaust passage L4 and flows into the diluter 5. Unreacted hydrogen flows through the hydrogen exhaust passage L5, and a part of the unreacted hydrogen merges with the hydrogen in the hydrogen supply passage L2 via the hydrogen circulation passage L6 and flows into the fuel cell stack 1 again. Then, the remaining hydrogen flowing through the hydrogen exhaust passage L5 flows into the diluter 5, is diluted by the air flowing from the air exhaust passage L4, and is discharged to the outside.

When the operation of the fuel cell system 100 is stopped, that is, when the fuel cell stack 1 is stopping power generation, the injector 4, the hydrogen shutoff valve 12, the pressure reducing valve 13, the air pressure regulating valve 14, the hydrogen exhaust valve 15, and the air shutoff valve 16 are provided. Is in the closed state. Hydrogen remains in the hydrogen supply passage L2 and the bypass passage L3. Here, as shown in FIG. 2, when the fuel cell system 100 has stopped operating, that is, in a state where the fuel cell stack 1 has stopped power generation, the first hydrogen pressure P _M second hydrogen pressure P _The pressure becomes higher than _L. Further, the relief valve 11 of the bypass passage L3, when the pressure difference between the first hydrogen pressure P _M and the downstream of the second hydrogen pressure P _L on the upstream is equal to or greater than the predetermined pressure Pc as switched from a closed state to an open state I do. Here, if the maximum pressure differential between the second hydrogen pressure P _L of the first hydrogen pressure P _M and the downstream of the upstream injector 4 during the power generation of the fuel cell stack 1 and the power generation at the maximum pressure difference dP1, pressure Pc is larger than the maximum pressure difference during power generation dP1. Thus, when the fuel cell stack 1 is generating power, the relief valve 11 does not open. In other words, the predetermined pressure Pc (cracking pressure of the relief valve 11) is determined in this way.

Further, when air enters the fuel cell stack 1 while the power generation of the fuel cell stack 1 is stopped, oxygen contained in the infiltrated air reacts with hydrogen remaining in the fuel cell stack 1 to produce water. Is done. Then, correspondingly, as shown in FIG. 2, the second hydrogen pressure P _L of the inlet of the anode side of the fuel cell stack 1 is gradually reduced. As a result, the differential pressure between the first hydrogen pressure P _M and the second hydrogen pressure P _L after lapse of time t1 reaches the pressure Pc, the relief valve 11 is opened. Then, the hydrogen remaining on the upstream side of the injector 4 is supplied to the downstream side of the injector 4, that is, the inlet on the anode side of the fuel cell stack 1 via the bypass flow path L <b> 3. Thus, the first hydrogen pressure P _M decreases, since the second hydrogen pressure P _L increases, the relief valve 11 a differential pressure between the first hydrogen pressure P _M and the second hydrogen pressure P _L is smaller than the pressure Pc is It is closed again.

Then, again the second hydrogen pressure P _L gradually decreases, the differential pressure between the first hydrogen pressure P _M and the second hydrogen pressure P _L reaches the pressure Pc after the elapsed time t2, the relief valve 11 is opened State. Thereafter, the relief valve 11 again differential pressure between the first hydrogen pressure P _M and the second hydrogen pressure P _L is smaller than the pressure Pc is closed. Further, after a lapse of time t3, the relief valve 11 performs an operation of switching between the open state and the closed state according to the same principle. That is, as shown in FIG. 2, after the relief valve 11 has been switched from a closed state to an open state at a substantially constant period, immediately become closed again, each time, the second with the first hydrogen pressure P _M decreases hydrogen pressure P _L is temporarily increased.

Thus, the fuel cell system 100 according to this embodiment has a relief valve 11 in the bypass passage L3 which bypasses the injectors 4, the relief valve 11 and the first hydrogen pressure P _M and the second hydrogen pressure P _L When the differential pressure exceeds the predetermined pressure Pc, the state is switched from the closed state to the open state. Thus, as shown in FIG. 2, the second hydrogen pressure P _L is in a range not reaching the lower limit pressure P _LL, hydrogen remaining in the upstream of the injector 4 is supplied to the fuel cell stack 1. Therefore, the oxygen in the air that has entered the fuel cell stack 1 from the exhaust side is consumed by reacting with the hydrogen supplied to the fuel cell stack 1, thereby preventing deterioration and performance deterioration due to oxidation of the fuel cell stack 1. Is done. Further, the relief valve 11 to open and close in response to differential pressure between the first hydrogen pressure P _M and the second hydrogen pressure P _L, or electrically controlling the opening and closing of the relief valve 11, a first hydrogen pressure P _M there is no need or monitored using and sensor a second hydrogen pressure P _L. Therefore, in the fuel cell system 100, since the performance of the fuel cell stack 1 can be reliably prevented from deteriorating with a simple structure, the structure of the fuel cell system 100 is complicated, and the sealing of the air pressure regulating valve 14 on the exhaust side is prevented. There is no need to improve performance.

The configuration is not limited to the configuration of the fuel cell system 100 shown in FIG. 1. As in the fuel cell system 200 shown in FIG. 2, the bypass flow path L <b> 3 is provided with a bypass-side cutoff valve 21 upstream of the relief valve 11. It may be. The bypass-side cutoff valve 21 is closed when the vehicle key is ON, that is, when the fuel cell stack 1 is generating power, and when the vehicle key is OFF, that is, when the fuel cell stack 1 stops generating power. When open, it is open. Thus, it is possible to prevent the relief valve 11 from being opened during the operation of the fuel cell system 100. Since it is not necessary to set larger than the pressure Pc necessarily power the maximum pressure difference dP1, freer first hydrogen pressure P _M and the variation range of the second hydrogen pressure P _L in the power generation stop of the fuel cell stack 1 Can be set to

Further, in the fuel cell systems 100 and 200, the hydrogen cutoff valve 12 and the pressure reducing valve 13 may be kept open while the power generation of the fuel cell stack 1 is stopped. Thus, always hydrogen is supplied to the upstream of the injector 4, a first hydrogen pressure P _M also when the relief valve 11 is in the open state constant pressure without lowering is maintained. Further, the time during which the performance of the fuel cell stack 1 can be prevented from deteriorating when power generation is stopped is further extended.

  DESCRIPTION OF SYMBOLS 1 Fuel cell stack, 3 hydrogen tank, 4 injectors (pressure regulator), 11 relief valve, 21 bypass side shutoff valve (shutoff valve), 100, 200 fuel cell system, L2 hydrogen supply flow path, L3 bypass flow path, Pc Predetermined pressure.

Claims (2)

A fuel cell stack that generates electricity by reacting hydrogen with oxygen in the air,
A hydrogen tank that supplies the hydrogen to the fuel cell stack;
A hydrogen supply channel provided between the fuel cell stack and the hydrogen tank, through which the hydrogen flows;
A pressure adjusting device provided in the hydrogen supply channel to adjust the pressure of the hydrogen flowing into the fuel cell stack;
A bypass flow path that bypasses the pressure regulator and is connected to the hydrogen supply flow path;
A relief valve provided in the bypass flow path ,
A shutoff valve provided in the bypass flow path ,
In the bypass passage, the pressure of the hydrogen upstream of the relief valve is higher than the pressure of the hydrogen downstream of the relief valve, and the pressure of the hydrogen upstream of the relief valve and the pressure of the hydrogen downstream of the relief valve. when there is a pressure differential on a predetermined pressure or higher between the pressure of the hydrogen, the relief valve is Ri Do opened,
The fuel cell system, wherein the shut-off valve is in a closed state during power generation of the fuel cell stack, and is in an open state when power generation of the fuel cell stack is stopped . The fuel cell system according to claim 1 , wherein the pressure adjusting device is an injector .

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