JP2009004169A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of changing air flow channels even in the case a pressure loss is small at a bypass channel, in a system equipped with a bypass channel bypassing a cooling unit. <P>SOLUTION: The fuel cell system 1 is provided with a bypass tube 31 communicating an upstream side and a downstream side of the cooling unit 22 out of an air supply tube 23, a bypass valve 32 fitted to the air supply tube 23 for adjusting an air volume flowing in the cooling unit 22, a check valve 33 fitted in free opening and closing to the bypass tube 31 and opening when a difference between an internal pressure and a back pressure of the bypass tube 31 exceeds a given value, a back pressure guide tube 34 guiding in the internal pressure at a downstream side of the cooling unit 22 of the air supply tube 23 as a back pressure of the check valve 33, an atmospheric air opening tube 35 communicating the back pressure guide tube 34 with the outside, and a relief valve 351 fitted to the atmospheric air opening tube 35 for opening and closing the atmospheric air opening tube 35. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system. Specifically, the present invention relates to a fuel cell system having a function of bypassing a cooler that cools air.

  In recent years, fuel cell systems have attracted attention as a new power source for automobiles. The fuel cell system includes, for example, a fuel cell that generates power by chemically reacting a reaction gas, a reaction gas supply device that supplies the reaction gas to the fuel cell via a reaction gas flow path, and a control that controls the reaction gas supply device. An apparatus.

  The fuel cell has, for example, a stack structure in which several tens to several hundreds of cells are stacked. Here, each cell is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators. The membrane electrode structure includes two electrodes, an anode electrode (anode) and a cathode electrode (cathode), and these electrodes. And a solid polymer electrolyte membrane sandwiched between the two.

  When hydrogen gas as a reaction gas is supplied to the anode electrode of the fuel cell and air containing oxygen as a reaction gas is supplied to the cathode electrode, power is generated by an electrochemical reaction. Since only harmless water is generated at the time of power generation, fuel cells are attracting attention from the viewpoint of environmental impact and utilization efficiency.

  Here, the air supplied to the cathode electrode is conventionally taken from air in the atmosphere. Specifically, a compressor is provided in the fuel cell system, and air in the atmosphere is pumped by the compressor to supply an amount of air necessary for power generation to the cathode electrode. However, if the compressed air whose temperature has been raised continues to be supplied to the fuel cell, the above-described electrolyte membrane will deteriorate, so a cooler for cooling the compressed air is provided on the passage through which the air flows. It is done.

  By the way, when the fuel cell system is started at a low temperature, it is necessary to warm the fuel cell until stable power generation is possible. In view of this, Patent Document 1 discloses a fuel cell system including a bypass mechanism that bypasses a cooler and supplies air. This bypass mechanism includes a bypass passage that bypasses the cooler provided in the main flow path, and a bypass valve provided on the outlet side of the cooler. Further, in this bypass mechanism, a bypass valve is provided as a check valve that opens and closes by the difference between the internal pressure of the bypass passage and the back pressure, and the pressure downstream of the cooler in the main flow path is introduced as the back pressure of the check valve. A signal pressure passage is provided.

According to this bypass mechanism, by supplying air with the bypass valve opened, the supplied air is supplied to the fuel cell through the cooler. At this time, since the pressure in the signal pressure passage is substantially equal to the pressure on the upstream side of the bypass passage, the check valve remains closed, and the compressed air flows only through the main passage.
Also, if air is supplied with the bypass valve closed, the pressure in the signal pressure passage is lower than the pressure upstream of the bypass passage due to pressure loss in the bypass passage, so the check valve is open and compressed. Air will circulate only in the bypass passage.

Here, for example, when starting the fuel cell system at a low temperature, by supplying air with the bypass valve closed, by supplying compressed air to the fuel cell through the bypass passage, The warming up of the fuel cell can be promoted.
JP 2004-139866 A

  However, when the flow rate of air supplied from the compressor is small, such as immediately after the start of the fuel cell, the pressure loss in the bypass passage is small, so there is a difference between the pressure in the bypass passage and the pressure in the signal pressure passage. May not occur and the check valve may not open.

  In such a case, the check valve can be opened by increasing the difference between the pressure in the bypass passage and the pressure in the signal pressure passage by increasing the air flow rate, but supply more air than necessary. Therefore, the power consumption of the compressor may increase. For this reason, when such a fuel cell system is mounted in an automobile, the fuel consumption of the automobile may be reduced.

  An object of the present invention is to provide a fuel cell system that includes a bypass passage that bypasses a cooler, and that can switch the air flow path even when the pressure loss in the bypass passage is small. To do.

  The fuel cell system of the present invention includes a fuel cell (for example, a fuel cell 10 described later) that generates power using a reaction gas, a main channel (for example, an air supply pipe 23 described later) for introducing the reaction gas into the fuel cell, A reaction gas supply device (for example, a compressor 21 to be described later) that supplies reaction gas to the fuel cell via the main flow path and a state of the reaction gas that is provided in the main flow path and flows through the main flow path are changed. A state change device (for example, a cooler 22 described later), a bypass flow channel (for example, a bypass tube 31 described later) communicating with the upstream side and the downstream side of the state change device in the main flow channel, and the main flow channel A bypass adjustment valve (for example, a bypass valve 32 described later) that adjusts the amount of reaction gas flowing through the state change device, and an internal pressure and a back pressure of the bypass flow path that can be opened and closed. A check valve (for example, a check valve 33 to be described later) that opens when the difference between the first flow rate and the difference exceeds a predetermined value, and an internal pressure downstream of the state change device in the main flow path is introduced as a back pressure of the check valve. A connection channel (for example, a back pressure introduction pipe 34 described later), a second connection channel (for example, an atmosphere release pipe 35 described later) communicating the first connection channel and the outside, and the second And a relief valve (for example, a relief valve 351 described later) that opens and closes the second connection channel.

According to the present invention, the pressure of the gas supplied from the reaction gas supplier is introduced into the check valve as the operating pressure, and the pressure downstream of the main channel state change device is the first connection channel. Introduced as back pressure through.
Here, since the second connecting flow path and the relief valve are provided, when the relief valve is closed, the pressure on the downstream side of the state change device of the main flow path is introduced as a back pressure to the check valve. . From this state, by opening the relief valve, the first connection channel can be opened to the atmosphere, and atmospheric pressure can be introduced into the check valve as a back pressure. That is, by opening the relief valve, the back pressure introduced into the check valve is assisted, and the difference between the operating pressure and the back pressure can be increased. As a result, the check valve can be opened with a slight operating pressure.

As described above, since the back pressure introduced into the check valve can be assisted by opening the relief valve, the check valve can be reduced in size.
In addition, since the check valve can be opened even with a slight operating pressure, the reaction gas can be bypassed even when the amount of reaction gas supplied is small, and the pressure loss in the check valve can be reduced to reduce the reaction gas supply machine. Power consumption can be reduced.

  In this case, it is preferable that an orifice (for example, an orifice 341 described later) is provided in the first connection channel.

  According to the present invention, by providing the orifice in the first connection channel, the pressure introduced as the back pressure into the check valve can be reduced, and the check valve can be easily held in the open state. Further, when the relief valve is opened, the amount of reaction gas discharged from the main flow path to the atmosphere via the first connection flow path and the second connection flow path can be reduced.

  According to the fuel cell system of the present invention, by opening the relief valve, the back pressure introduced into the check valve can be assisted to increase the difference between the operating pressure and the back pressure. As a result, the check valve can be opened with a slight operating pressure. Moreover, since the back pressure introduced into the check valve can be assisted by opening the relief valve, the check valve can be reduced in size. In addition, since the check valve can be opened even with a slight operating pressure, the reaction gas can be bypassed even when the amount of reaction gas supplied is small, and the pressure loss in the check valve can be reduced to reduce the reaction gas supply machine. Power consumption can be reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a fuel cell system 1 according to the present embodiment.
The fuel cell system 1 includes a fuel cell 10, a supply device 20 for supplying hydrogen gas and air (air) as reaction gas to the fuel cell 10, and a control device 40 for controlling the fuel cell 10 and the supply device 20. Have

  The fuel cell 10 has a stack structure in which, for example, several tens to several hundreds of cells are stacked. Each cell is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators. The membrane electrode structure is composed of two electrodes, an anode electrode (anode) and a cathode electrode (cathode), and a solid polymer electrolyte membrane sandwiched between these electrodes. Usually, both electrodes are formed of a catalyst layer that performs an oxidation / reduction reaction in contact with the solid polymer electrolyte membrane and a gas diffusion layer in contact with the catalyst layer. Such a fuel cell 10 generates power by these electrochemical reactions when hydrogen gas is supplied to the anode electrode (anode) side and air containing oxygen is supplied to the cathode electrode (cathode) side.

  The fuel cell 10 is connected to a motor 13 and a high voltage battery (not shown) through a current limiter (VCU) 12 that limits the output of the fuel cell 10. The electric power generated by the fuel cell 10 is supplied to the motor 13 and the high voltage battery. Based on the current limit value output from the control device 40, the current limiter 12 limits the current extracted from the fuel cell 10 within the range of the current limit value, and supplies the electric power of the fuel cell 10 to the motor 13 and the high voltage. Supply to battery.

  The supply device 20 includes a compressor 21 as a reaction gas supply device that supplies air to the cathode electrode side of the fuel cell 10, and an ejector 28 that supplies hydrogen gas to the anode electrode side.

  The ejector 28 is provided on a hydrogen circulation path 25 including the anode electrode side of the fuel cell 10 in its path, and circulates hydrogen gas supplied from a hydrogen tank (not shown) on the hydrogen circulation path 25. The hydrogen circulation path 25 is formed by branching a hydrogen discharge path 26 for exhausting the gas in the hydrogen circulation path 25 to the outside. A purge valve 261 is provided at the front end side of the hydrogen discharge path 26.

  The compressor 21 is connected to the cathode electrode side of the fuel cell 10 via an air supply pipe 23 as a main flow path. The compressor 21 compresses air introduced from an air introduction pipe 27 that is open to the atmosphere, and supplies the compressed air to the fuel cell 10 via an air supply pipe 23. The compressor 21 operates in response to a command signal from the control device 40, compresses air at a set compression ratio, and supplies the air to the air supply pipe 23.

  An air discharge pipe 24 for discharging the air introduced from the air supply pipe 23 is connected to the cathode electrode side of the fuel cell 10, and a back pressure valve 241 is provided on the tip side of the air discharge pipe 24.

  The air supply pipe 23 includes a cooler 22 as a state change device that changes the state of the air flowing through the air supply pipe 23 in order from the compressor 21 toward the fuel cell 10, and the air supply pipe 23. A humidifier 29 is provided for humidifying the air flowing therethrough.

  The cooler 22 is a heat exchanger, and cools the air supplied from the compressor 21 by heat exchange. Since the air compressed by the compressor 21 has a higher temperature than the state before compression, if the high-temperature air is directly introduced into a device such as the humidifier 29 or the fuel cell 10, these devices may be damaged. . In particular, among these devices, the below-described hollow fiber membrane provided in the humidifier 29 has the lowest heat-resistant temperature, that is, the permitted use temperature. Therefore, the air supply pipe 23 is provided with a cooler 22 to cool the air compressed to a high temperature and protect the humidifier 29 and the fuel cell 10.

  The humidifier 29 is a humidifier using a so-called hollow fiber membrane. Specifically, the humidifier 29 includes a bundle of water-permeable hollow fiber membranes and a housing that houses the hollow fiber membrane bundles. The air introduced into the humidifier 29 is humidified by exchanging moisture with the hollow fiber membrane bundle inside the housing. The fuel cell 10 is supplied with air humidified by the humidifier 29. The chemical reaction in the fuel cell 10 is performed by the MEA membrane as described above. If the humidity of the MEA membrane cannot be secured to some extent, the exchange of ions is not performed. Therefore, by humidifying the air with the humidifier 29, Ensure a certain level of MEA humidity.

  By the way, when the fuel cell system 1 is started, if the fuel cell 10 is in a low temperature state, the fuel cell 10 needs to be warmed up to a temperature suitable for power generation. For this reason, when the fuel cell system 1 is started at a low temperature, the air compressed by the compressor 21 is not cooled by the cooler 22 in order to promote the warm-up, and the humidifier 29 and the fuel cell 10 are left as they are. It may be preferable to introduce into Therefore, the air supply pipe 23 is provided with a bypass mechanism 30 that bypasses the cooler 22.

  FIG. 2 is a block diagram showing the configuration of the bypass mechanism 30, and shows a state in which air is supplied via the cooler 22. FIG. 3 is a block diagram showing the configuration of the bypass mechanism 30, and shows a state in which air is supplied by bypassing the cooler 22.

  The bypass mechanism 30 includes a bypass pipe 31 as a bypass flow path, a bypass valve 32 as a bypass adjustment valve, a check valve 33, a back pressure introduction pipe 34 as a first connection flow path, and a second connection flow. And an open air pipe 35 as a road.

The bypass pipe 31 is connected to the air supply pipe 23 and communicates the upstream side and the downstream side of the cooler 22. Further, the flow path of the bypass pipe 31 is narrower than the flow path of the air supply pipe 23.
The bypass valve 32 is provided in the air supply pipe 23 on the downstream side of the cooler 22 and on the upstream side of the junction point between the bypass pipe 31 and the air supply pipe 23, and the amount of air flowing through the cooler 22 is reduced. adjust.

  The check valve 33 is provided in the bypass pipe 31 and opens and closes the bypass pipe 31. The back pressure introducing pipe 34 connects the downstream side of the check valve 33 in the bypass pipe 31 and the second cylindrical portion 335 side (described later) of the check valve 33. As a result, the back pressure introduction pipe 34 introduces the internal pressure downstream of the cooler 22 of the air supply pipe 23 into the check valve 33 as a back pressure. The back pressure introduction pipe 34 is provided with an orifice 341 that restricts the flow path of the back pressure introduction pipe 34. By providing such an orifice 341, the pressure acting as a back pressure on the check valve 33 can be reduced.

Check valve 33 opens and closes the internal pressure _{P 1} of the bypass pipe 31 as the working pressure. More specifically, the check valve 33 is closed when the difference between the internal pressure P ₁ of the bypass pipe 31 and the back pressure P ₂ introduced by the back pressure introduction pipe 34 is less than a predetermined value, and when the check valve 33 becomes a predetermined value or more. open. Specifically, the check valve 33 includes a cylindrical valve main body 331, a piston 332 provided inside the valve main body 331 so as to be able to advance and retreat, and a spring mechanism 333 that urges the piston.

The valve main body 331 includes a cylindrical first cylindrical portion 334 and a second cylindrical portion 335 connected to the first cylindrical portion 334. A diaphragm 336 is provided between the first cylindrical portion 334 and the second cylindrical portion 335.
The piston 332 includes a diaphragm 336 that is provided inside the second cylindrical part and partitions the inside of the second cylindrical part, and a rod 337 provided on the diaphragm 336.
The spring mechanism 333 biases the piston 332 in a direction to close the valve body 331.

The air supply pipe 23 is connected to an opening on the first cylindrical portion 334 side of the valve body 331, the back pressure introduction pipe 34 is connected to an opening on the second cylindrical portion 335 side of the valve body 331, and the bypass pipe 31 is The first cylindrical portion 334 is connected to the vicinity of the diaphragm 336. Thereby, the inside of the first cylindrical portion 334 becomes the internal pressure P ₁ of the bypass pipe 31, and the inside of the second cylindrical portion 335 becomes the back pressure P ₂ introduced by the back pressure introducing pipe 34.

The operation of the check valve 33 is as follows.
That is, in the check valve 33, when the difference between _{P 1} and _{P 2} is less than the predetermined value, the spring mechanism 333, by the piston 332 in the direction of closing the valve body 331 is energized, the first cylindrical by the diaphragm 336 The part 334 is closed. As a result, the bypass pipe 31 is closed.
On the other hand, if the difference between P ₁ and P ₂ becomes equal to or higher than a predetermined value, this pressure difference, to resist the biasing force of the spring mechanism 333, the piston 332 is retracted, opening the valve body 331. As a result, the bypass pipe 31 is opened.

The air release pipe 35 communicates the back pressure introduction pipe 34 with the outside opened to the atmospheric pressure. The relief valve 351 is provided in the atmosphere release pipe 35 and opens and closes the atmosphere release pipe 35. That is, by opening the relief valve 351 and communicating the back pressure introduction pipe 34 with the outside, the back pressure P ₂ of the check valve 33 is lowered to the vicinity of the atmospheric pressure, and the difference between P ₁ and P ₂ is increased. The operation of the valve 33 can be assisted.

Next, the operation of the bypass mechanism 30 configured as described above will be described.
As shown in FIG. 2, when the air compressed by the compressor 21 is circulated to the cooler 22, the bypass valve 32 is opened and the relief valve 351 is closed.
Then, the air compressed by the compressor 21 flows through the air supply pipe 23. In this state, the back pressure P ₂ that is introduced by the internal pressure P ₁ and the back-pressure pipe 34 of the bypass pipe 31 is approximately equal, the check valve 33 is maintained in the closed state. Therefore, the bypass pipe 31 is in a closed state, and air circulates only through the cooler 22.
When the fuel cell system 1 is normally operated, the humidifier 29 and the bypass valve 32 are opened and the relief valve 351 is closed as described above, and air is supplied via the cooler 22. The operation can be continued by setting the fuel cell 10 to a temperature lower than the heat resistant temperature.

As shown in FIG. 3, when the air compressed by the compressor 21 is circulated through the bypass pipe 31, the bypass valve 32 is closed and the relief valve 351 is opened.
Then, the back pressure P ₂ that is introduced by back-pressure pipe 34, a pressure close to atmospheric pressure. In contrast, the internal pressure P ₁ are the pressure of the compressed air in the compressor 21 is higher than the atmospheric pressure. Therefore, a large difference occurs between P ₁ and P ₂ , and the check valve 33 is held open. Therefore, the bypass pipe 31 is held in an open state, and air flows through the bypass pipe 31.
When the fuel cell system 1 is started at a low temperature, the bypass valve 32 is closed and the relief valve 351 is opened as described above, and air is supplied by bypassing the cooler 22, thereby It can promote warm-up.

By the way, immediately after the fuel cell system 1 is started, while the fuel cell 10 is warmed up, the flow rate of air is particularly small, so that the pressure loss in the bypass pipe 31 is small and P ₁ and P ₂ And the check valve 33 may be difficult to open. Therefore, as described above, closes the bypass valve 32 opens the relief valve 351, by increasing the difference between the P ₁ and P _2, it can be operated reliably check valve 33. Further, even if the air flow rate is high, open the relief valve 351, by increasing the difference between P ₁ and P _2, it can be reduced pressure loss in the check valve 33. Thereby, the power consumption of the compressor 21 can be reduced.

  Returning to FIG. 1, the control device 40 includes devices such as the VCU 12, the compressor 21, the back pressure valve 241, the purge valve 261, and the bypass valve 32 that are driven based on a control signal output from the control device 40. Is connected.

  The control device 40 is connected with an ignition switch (not shown). This ignition switch is provided in the driver's seat of the fuel cell vehicle, and transmits an on / off signal to the control device 40 in accordance with the operation of the driver. The control device 40 generates power from the fuel cell 10 in accordance with ON / OFF of the ignition switch.

Here, based on the ignition switch being turned on, the procedure for generating power by the fuel cell 10 by the control device 40 is as follows.
That is, hydrogen gas is supplied from a hydrogen tank (not shown) to the anode side of the fuel cell 10 via the ejector 28. Further, by driving the compressor 21, air is supplied to the cathode side of the fuel cell 10 through the air supply pipe 23.
The hydrogen gas and air supplied to the fuel cell 10 are supplied to the power generation, and then flow into the hydrogen discharge path 26 and the air discharge pipe 24 together with residual water such as produced water on the anode side from the fuel cell 10. These hydrogen gas and air are processed by an exhaust gas processing device (not shown) and discharged outside.

According to the fuel cell system 1 of the present embodiment, there are the following effects.
(1) The pressure of the air supplied from the compressor 21 is introduced into the check valve 33 as an operating pressure, and the pressure downstream of the cooler 22 of the air supply pipe 23 passes through the back pressure introduction pipe 34. It is introduced as back pressure.
Here, since the air release pipe 35 and the relief valve 351 are provided, when the relief valve 351 is closed, the pressure on the downstream side of the cooler 22 of the air supply pipe 23 relative to the check valve 33 is the back pressure. be introduced. From this state, by opening the relief valve 351, the back pressure introduction pipe 34 can be opened to the atmosphere, and atmospheric pressure can be introduced into the check valve 33 as back pressure. That is, by opening the relief valve 351, the back pressure introduced into the check valve 33 can be assisted to increase the difference between the operating pressure and the back pressure. As a result, the check valve 33 can be opened with a slight operating pressure.

As described above, since the back pressure introduced into the check valve 33 can be assisted by opening the relief valve 351, the check valve 33 can be reduced in size.
In addition, since the check valve 33 can be opened even with a slight operating pressure, the air can be bypassed even if the amount of air supplied is small, and the pressure loss in the check valve 33 can be reduced, so that the compressor 21 Power consumption can be reduced.

  (2) By providing the orifice 341 in the back pressure introduction pipe 34, the pressure introduced as the back pressure into the check valve 33 can be reduced, and the check valve 33 can be easily held in the open state. Further, when the relief valve 351 is opened, the amount of air discharged from the air supply pipe 23 to the atmosphere through the back pressure introduction pipe 34 and the atmosphere release pipe 35 can be reduced.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements and the like within a scope that can achieve the object of the present invention are included in the present invention.

It is a block diagram which shows the structure of the fuel cell system which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the bypass mechanism which concerns on the said embodiment. It is a block diagram which shows the structure of the bypass mechanism which concerns on the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 20 Supply apparatus 21 Compressor (reactive gas supply machine)
22 Cooler (state change device)
23 Air supply pipe (main flow path)
29 Humidifier 30 Bypass mechanism 31 Bypass pipe (bypass flow path)
32 Bypass valve (Bypass adjustment valve)
33 Check valve 34 Back pressure introduction pipe (first connecting flow path)
341 Orifice 35 Open air pipe (second connecting flow path)
351 Relief valve (Relief valve)

Claims (2)

A fuel cell that generates power using reactive gas;
A main flow path for introducing a reaction gas into the fuel cell;
A reaction gas supplier for supplying a reaction gas to the fuel cell via the main flow path;
A state change device that is provided in the main flow path and changes the state of the reaction gas flowing through the main flow path;
A bypass channel that communicates the upstream side and the downstream side of the state change device in the main channel;
A bypass adjustment valve that is provided in the main flow path and adjusts the amount of reaction gas flowing through the state change device;
A check valve provided in the bypass channel so as to be openable and closable, and opened when a difference between the internal pressure and the back pressure of the bypass channel becomes a predetermined value or more;
A first connection channel that introduces an internal pressure downstream of the state change device of the main channel as a back pressure of the check valve;
A second connection channel that communicates the first connection channel with the outside;
A fuel cell system comprising: a relief valve that is provided in the second connection channel and opens and closes the second connection channel.   The fuel cell system according to claim 1, wherein an orifice is provided in the first connection channel.

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