JP2007317472A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system enhancing sound deadening effect during opening of a bypass valve. <P>SOLUTION: In the fuel cell system equipped with a bypass passage 17 connecting a supply passage 11 and an exhaust passage 12 so that oxidative gas flows by bypassing a fuel cell 2; a bypass valve 18 opening and closing the bypass passage 17, the length of at least one of the supply passage 11, the exhaust passage 12 and the bypass passage 17 is adjusted so that the oxidative gas and oxidative offgas, their phases are shifted each other, are joined during opening of the bypass valve 18. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system capable of bypassing an oxidizing gas to a fuel cell.

  A fuel cell mounted on a fuel cell vehicle or the like generates electric power by a chemical reaction between hydrogen in fuel gas supplied to the anode and oxygen in oxidizing gas supplied to the cathode. In general, the fuel off-gas discharged from the fuel cell passes through a hydrogen diluter and is discharged into the atmosphere with a reduced hydrogen concentration. On the other hand, the oxidizing off gas discharged from the fuel cell is discharged directly into the atmosphere without passing through the diluter.

  However, when the fuel cell is operated with low power generation efficiency, not only hydrogen is discharged from the anode but also hydrogen (mainly pumping hydrogen) is discharged from the cathode. May contain hydrogen. In such a case, it is not environmentally preferable to discharge the oxidizing off gas to the atmosphere as it is.

As a fuel cell system capable of reducing the hydrogen concentration in the oxidizing off gas, for example, the one described in Patent Document 1 is known. This fuel cell system includes a bypass passage that communicates an oxidizing gas supply passage and an oxidizing off-gas exhaust passage, a bypass valve that opens and closes the bypass passage, and a silencer provided at a downstream end of the exhaust passage. The fuel cell system opens the bypass valve when the hydrogen concentration in the oxidizing off gas increases, and introduces the oxidizing gas into the oxidizing off gas by an air compressor, thereby reducing the hydrogen concentration in the oxidizing off gas. .
JP 2004-172027 A

  In such a conventional fuel cell system, during opening of the bypass valve, sound such as pulsation sound from the air compressor can be transmitted from the bypass path to the exhaust path without passing through the fuel cell. For this reason, when the oxidant gas and the oxidant off-gas merge while the bypass valve is opened, resonance may occur and a loud sound may be generated. However, the conventional fuel cell system is provided with a silencer. This silencer has a silencing effect when the exhaust gas is released into the atmosphere, and the sound that can be generated when the bypass valve is opened. Until then, it was not able to mute enough.

  An object of the present invention is to provide a fuel cell system capable of enhancing the silencing effect while the bypass valve is open.

  In order to achieve the above object, a fuel cell system according to the present invention includes a supply path through which an oxidizing gas supplied to a fuel cell flows, a supply device provided in the supply path, for pumping the oxidizing gas to the fuel cell, and a fuel cell. A fuel provided with a discharge path through which discharged oxidation off-gas flows, a bypass path that connects the supply path and the discharge path so that the oxidizing gas flows through the fuel cell, and a bypass valve that opens and closes the bypass path In the battery system, at least one of the supply path, the discharge path, and the bypass path is adjusted in pipe length so that the oxidant gas and the oxidant off-gas that are out of phase with each other are merged during the opening of the bypass valve. Is.

  According to such a configuration, the oxidizing gas and the oxidizing off gas that are out of phase with each other merge, so that the sound caused by the oxidizing gas and the sound caused by the oxidizing off gas can be attenuated so as to cancel each other. Thereby, it is possible to suppress the generation of a loud sound due to the merging of the oxidizing gas and the oxidizing off gas, and it is possible to enhance the silencing effect while the bypass valve is open. In addition, it is not necessary to provide a silencer or a sound source separately on the bypass path.

  Preferably, the fuel cell system of the present invention includes a control device that controls opening and closing of the bypass valve.

  According to this configuration, for example, the opening / closing of the bypass valve can be appropriately controlled according to the state of the fuel cell system.

  In order to achieve the above object, another fuel cell system of the present invention includes a supply path through which an oxidizing gas supplied to the fuel cell flows, a supply device provided in the supply path, for pumping the oxidizing gas to the fuel cell, a fuel A discharge path through which the oxidizing off-gas discharged from the battery flows, a bypass path that connects the supply path and the discharge path so that the oxidizing gas flows through the fuel cell, and a bypass valve that opens and closes the bypass path The fuel cell system further includes a control device that controls the opening and closing of the bypass valve so that resonance does not occur due to the merging of the oxidizing gas and the oxidizing off gas during the opening of the bypass valve.

  According to this configuration, since the bypass valve is controlled to open and close in consideration of resonance, it is possible to suppress generation of a loud sound due to the merging of the oxidizing gas and the oxidizing off gas. Thereby, even if a separate device (a silencer or a sound source) is not provided in the bypass path, the silencing effect while the bypass valve is open can be enhanced.

  Preferably, the control device controls the opening and closing of the bypass valve so as to skip a valve opening at which resonance occurs due to the merging of the oxidizing gas and the oxidizing off gas while the bypass valve is open.

  By doing so, the bypass valve can be opened and closed with a valve opening at which resonance does not occur.

  According to one aspect of the fuel cell system of the present invention described above, the control device preferably closes the bypass valve when the fuel cell system is in operation and opens the bypass valve when the fuel cell system is started. More preferably, the control device opens the bypass valve only when the fuel cell system is activated and at a predetermined low temperature.

  Further, according to another aspect of the fuel cell system of the present invention, the control device can open the bypass valve when performing the low-efficiency operation with a large power loss compared to the normal operation of the fuel cell system. preferable.

  According to this configuration, it is possible to dilute the oxidizing off gas with the oxidizing gas while enhancing the silencing effect even during low-efficiency power generation. Thereby, it can suppress that the fuel gas (for example, hydrogen gas) exceeding the regulation range is discharged | emitted from the discharge path outside.

  When the fuel cell system operates at low efficiency, self-heating of the fuel cell is promoted. Therefore, it is preferable that the low efficiency operation is performed only at a predetermined low temperature.

  According to this configuration, the fuel cell can be warmed up efficiently.

  The above-described fuel cell system of the present invention further includes a humidifier that is provided in a supply path on the downstream side of the supply machine and humidifies the oxidizing gas, and the supply-side connection portion between the supply path and the bypass path is more than the humidifier. It is preferable that it is located upstream.

  Moreover, it is preferable that the fuel cell system of the present invention further includes a pressure regulating valve provided in the discharge path.

  As described above, according to the fuel cell system of the present invention, it is possible to enhance the silencing effect while the bypass valve is open.

  Hereinafter, a fuel cell system according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. This fuel cell system can bypass the oxidizing gas with respect to the fuel cell, and is configured not to generate a loud sound due to the merging of the bypassed oxidizing gas and the oxidizing off gas.

<First Embodiment>
FIG. 1 is a configuration diagram of a fuel cell system 1.
The fuel cell system 1 of the present embodiment can be mounted on a vehicle such as a fuel cell vehicle (FCHV), an electric vehicle, and a hybrid vehicle. Of course, not only the vehicle but also various moving bodies (for example, ships, airplanes, robots, etc.) ) And stationary power sources.

  The fuel cell system 1 includes a fuel cell 2, an oxidizing gas piping system 3 that supplies air (oxygen) as an oxidizing gas to the fuel cell 2, and a fuel gas piping system that supplies hydrogen gas as a fuel gas to the fuel cell 2. 4, a refrigerant piping system 5 that supplies the refrigerant to the fuel cell 2 to cool the fuel cell 2, a power system 6 that charges and discharges the power of the system 1, and a control device 7 that performs overall control of the entire system. ing.

  The fuel cell 2 is formed of, for example, a solid polymer electrolyte type and has a stack structure in which a large number of single cells are stacked. The single cell has an air electrode (cathode) on one surface of an electrolyte made of an ion exchange membrane, a fuel electrode (anode) on the other surface, and a pair of the air electrode and the fuel electrode sandwiched from both sides. Of separators. An oxidizing gas is supplied to the oxidizing gas channel 2a of one separator, and a fuel gas is supplied to the fuel gas channel 2b of the other separator. The fuel cell 2 generates electric power by the electrochemical reaction of the supplied fuel gas and oxidizing gas. The electrochemical reaction in the fuel cell 2 is an exothermic reaction, and the temperature of the solid polymer electrolyte fuel cell 2 is approximately 60 to 80 ° C.

  The oxidizing gas piping system 3 includes a supply path 11 through which the oxidizing gas supplied to the fuel cell 2 flows, a discharge path 12 through which the oxidizing off gas discharged from the fuel cell 2 flows, and the oxidizing gas flows bypassing the fuel cell 2. And a bypass 17. The downstream end of the supply path 11 communicates with the upstream end of the oxidizing gas flow path 2a, and the upstream end of the discharge path 12 communicates with the downstream end of the oxidizing gas flow path 2a. The oxidizing off gas includes pumping hydrogen generated on the air electrode side of the fuel cell 2 (details will be described later). Further, the oxidizing off gas is in a highly moist state because it contains moisture generated by the cell reaction of the fuel cell 2.

  The supply path 11 is provided with a compressor 14 (feeder) that takes in the oxidizing gas (outside air) via the air cleaner 13 and a humidifier 15 that humidifies the oxidizing gas pumped to the fuel cell 2 by the compressor 14. Yes. The humidifier 15 exchanges moisture between the low-humidity oxidizing gas flowing in the supply passage 11 and the high-humidity oxidizing off-gas flowing in the discharge passage 12, and appropriately supplies the oxidizing gas supplied to the fuel cell 2. Humidify.

  The back pressure of the oxidizing gas supplied to the fuel cell 2 is regulated by a back pressure regulating valve 16 disposed in the discharge path 12 near the cathode outlet. In the vicinity of the back pressure adjusting valve 16, a pressure sensor P1 for detecting the pressure in the discharge passage 12 is provided. The oxidizing off gas passes through the back pressure regulating valve 16 and the humidifier 15 and is finally exhausted into the atmosphere outside the system as exhaust gas.

  The bypass path 17 connects the supply path 11 and the discharge path 12. A supply side connection B between the bypass path 17 and the supply path 11 is located between the compressor 14 and the humidifier 15. Further, the discharge side connection portion C between the bypass path 17 and the discharge path 12 is located on the downstream side of the humidifier 15. The bypass passage 17 is provided with a bypass valve 18 that is an on-off valve (shut valve) driven by a motor or a solenoid. The bypass valve 18 is connected to the control device 7 and opens and closes the bypass path 17. In the following description, the oxidizing gas that is bypassed downstream of the bypass passage 17 by opening the bypass valve 18 is referred to as “bypass air”.

  Since the differential pressure between the primary side and the secondary side of the bypass valve 18 is large, if there is a slight gap between the valve body and the valve seat when the bypass valve 18 is closed, the secondary pressure of the bypass valve 18 The amount of bypass air leakage to the side will increase. If the sealing effect when the bypass valve 18 is closed is not sufficient, the efficiency of the compressor 14 is reduced during normal operation in which the bypass valve 18 is closed (details will be described later). Therefore, as a preferred embodiment of the bypass valve 18, it is preferable to configure the poppet type having a self-sealing structure. By doing so, a large differential pressure between the primary side and the secondary side of the bypass valve 18 can be effectively used to enhance the sealing effect when the bypass valve 18 is closed.

  The fuel gas piping system 4 includes a hydrogen supply source 21, a supply path 22 through which hydrogen gas supplied from the hydrogen supply source 21 to the fuel cell 2 flows, and a supply path for supplying hydrogen offgas (fuel offgas) discharged from the fuel cell 2. 22, a circulation path 23 for returning to the junction point A of 22, a pump 24 that pumps the hydrogen off-gas in the circulation path 23 to the supply path 22, and a purge path 25 that is branched and connected to the circulation path 23. . The hydrogen gas flowing out from the hydrogen supply source 21 to the supply path 22 by opening the main valve 26 is supplied to the fuel cell 2 through the pressure regulating valve 27 and other pressure reducing valves and the shutoff valve 28. The purge passage 25 is provided with a purge valve 33 for discharging the hydrogen off gas to a hydrogen diluter (not shown).

  The refrigerant piping system 5 includes a refrigerant channel 41 communicating with the cooling channel 2 c in the fuel cell 2, a cooling pump 42 provided in the refrigerant channel 41, and a radiator 43 that cools the refrigerant discharged from the fuel cell 2. And a bypass passage 44 that bypasses the radiator 43, and a switching valve 45 that sets the flow of cooling water to the radiator 43 and the bypass passage 44. The refrigerant flow path 41 includes a temperature sensor 46 provided near the refrigerant inlet of the fuel cell 2 and a temperature sensor 47 provided near the refrigerant outlet of the fuel cell 2. The refrigerant temperature detected by the temperature sensor 47 reflects the internal temperature of the fuel cell 2 (hereinafter referred to as the temperature of the fuel cell 2). The cooling pump 42 circulates and supplies the refrigerant in the refrigerant channel 41 to the fuel cell 2 by driving the motor.

  The power system 6 includes a high-voltage DC / DC converter 61, a battery 62, a traction inverter 63, a traction motor 64, and various auxiliary inverters 65, 66, and 67. The high-voltage DC / DC converter 61 is a direct-current voltage converter that adjusts the direct-current voltage input from the battery 62 and outputs it to the traction inverter 63 side, and the direct-current input from the fuel cell 2 or the traction motor 64. And a function of adjusting the voltage and outputting it to the battery 62. The charge / discharge of the battery 62 is realized by these functions of the high-voltage DC / DC converter 61. Further, the output voltage of the fuel cell 2 is controlled by the high voltage DC / DC converter 61.

  The traction inverter 63 converts a direct current into a three-phase alternating current and supplies it to the traction motor 64. The traction motor 64 (power generation device) is, for example, a three-phase AC motor. The traction motor 64 constitutes, for example, a main power source of the vehicle 100 on which the fuel cell system 1 is mounted, and is connected to the wheels 101L and 101R of the vehicle 100. The auxiliary machine inverters 65, 66, and 67 control the driving of the motors of the compressor 14, the pump 24, and the cooling pump 42, respectively.

  The control device 7 is configured as a microcomputer having a CPU, ROM, and RAM therein. The CPU performs desired processing according to the control program, and performs various processes and controls such as control of low-efficiency operation described later. The ROM stores control programs and control data processed by the CPU. The RAM is mainly used as various work areas for control processing.

  The control device 7 includes a pressure sensor (P1) and temperature sensors (46, 47) used in the gas system (3, 4) and the refrigerant system 5, and an outside air temperature sensor that detects the outside air temperature in the environment where the fuel cell system 1 is placed. 51, and detection signals from various sensors such as an accelerator opening sensor that detects the accelerator opening of the vehicle 100 are input, and a control signal is output to each component. In addition, when it is necessary to warm up the fuel cell 2 such as when starting at a low temperature, the control device 7 performs an operation with low power generation efficiency using various maps stored in the ROM.

  FIG. 2 is a diagram showing the relationship between the output current (hereinafter referred to as “FC current”) of the fuel cell 2 and the output voltage (hereinafter referred to as “FC voltage”). FIG. 2 shows the case where the fuel cell system 1 is operated with relatively high power generation efficiency (hereinafter referred to as “normal operation”) as a solid line, and the fuel cell system 1 is operated with relatively low power generation efficiency (hereinafter referred to as “normal operation”). The case of “low efficiency operation”) is indicated by a dotted line.

  When the fuel cell system 1 is normally operated, the fuel cell 2 is operated in a state where the air stoichiometric ratio is set to 1.0 or more (theoretical value) so that high power generation efficiency can be obtained while suppressing power loss (see FIG. (See solid line part 2). Here, the air stoichiometric ratio means an oxygen surplus ratio, and indicates how much oxygen is supplied to oxygen necessary for reacting with hydrogen without excess or deficiency.

  On the other hand, when the fuel cell 2 is warmed up, the fuel cell 2 is set with the air stoichiometric ratio set to less than 1.0 (theoretical value) in order to increase the power loss and raise the temperature of the fuel cell 2. (See the dotted line portion in FIG. 2). When the air stoichiometric ratio is set to a low value and the low efficiency operation is performed, the power loss (that is, the heat loss) of the energy that can be extracted by the reaction between hydrogen and oxygen is positively increased. While it is possible to warm up, pumping hydrogen is generated at the air electrode of the fuel cell 2.

3A and 3B are diagrams for explaining the generation mechanism of pumping hydrogen, in which FIG. 3A shows a battery reaction during normal operation, and FIG. 3B shows a battery reaction during low-efficiency operation.
Each single cell 80 of the fuel cell 2 includes an electrolyte membrane 81 and an anode and a cathode that sandwich the electrolyte membrane 81. A fuel gas containing hydrogen (H ₂ ) is supplied to the anode, and an oxidizing gas containing oxygen (O ₂ ) is supplied to the cathode. When fuel gas is supplied to the anode, the reaction of the following formula (1) proceeds, and hydrogen is separated from hydrogen ions and electrons. Hydrogen ions generated at the anode pass through the electrolyte membrane 81 and move to the cathode, while electrons move from the anode through the external circuit to the cathode.
Anode: H ₂ → 2H ⁺ + 2e ⁻ (1)

Here, in the case of the normal operation shown in FIG. 3A, that is, when the supply of the oxidizing gas to the cathode is sufficient (air stoichiometric ratio ≧ 1.0), the following equation (2) proceeds and oxygen, hydrogen Water is produced from ions and electrons.
Cathode: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)

On the other hand, in the case of the low-efficiency operation shown in FIG. 3B, that is, when the supply of the oxidizing gas to the cathode is insufficient (air stoichiometric ratio <1.0), the following formula is set according to the insufficient oxidizing gas amount. (3) proceeds and hydrogen ions and electrons recombine to generate hydrogen. The produced hydrogen is discharged from the cathode together with the oxidizing off gas. Note that hydrogen generated at the cathode by recombination of dissociated hydrogen ions and electrons, that is, the anode gas generated at the cathode is called pumping hydrogen.
Cathode: 2H ⁺ + 2e ⁻ → H ₂ (3)

  Thus, in a state where supply of the oxidizing gas to the cathode is insufficient, pumping hydrogen is included in the oxidizing off gas. Therefore, when the fuel cell system 1 performs low-efficiency operation, the control device 7 controls the opening of the bypass valve 18 so that a part of the oxidizing gas supplied by the compressor 13 is diverted to the bypass passage 17. Yes. The dilute bypass air dilutes the hydrogen concentration in the oxidation off gas, and the oxidation off gas with the hydrogen concentration reduced to a safe range is exhausted from the discharge path 12 to the outside.

  The low-efficiency operation is performed at the time of starting the fuel cell system 1 mainly for the purpose of warming up the fuel cell 2, and is performed only at the time of starting at a low temperature. For example, when the outside air temperature detected by the outside air temperature sensor 51 at the start of the fuel cell system 1 is a predetermined low temperature (for example, 0 ° C. or less), the fuel cell system 1 is operated at a low efficiency. When the warm-up of the fuel cell 2 is completed, the fuel cell system 1 shifts from the low efficiency operation to the normal operation. The bypass valve 18 is opened when the fuel cell system 1 that performs low-efficiency operation is started, and is closed during normal operation after the low-efficiency operation.

However, in other embodiments, the bypass valve 18 may be opened during normal operation. A preferred example will be described.
When the traction motor 64 functions as a generator and performs regenerative braking, such as when the vehicle 100 is decelerated, the output of the fuel cell 2 is stopped and the battery 62 is charged with electric power (regenerative power). However, when the amount of charge of the battery 62 is full during regeneration, the regenerative power in the electric power system 6 becomes a surplus state. Therefore, when the battery 62 cannot be charged during regeneration, the compressor 14 is driven excessively to consume excess regeneration power, and the bypass valve 18 is opened to cause excess oxidizing gas to be generated in the fuel cell 2. It is preferable not to supply.

FIG. 4 is an enlarged configuration diagram showing the oxidizing gas piping system 3.
As described above, when the bypass valve 18 is opened, the oxidizing gas is diverted at the supply side connecting portion B, and a part of the oxidizing gas flows to the discharge side connecting portion C as bypass air, while the remaining oxidizing gas remains. Is supplied to the oxidizing gas flow path 2a in the fuel cell 2 as a reaction gas. The oxidizing off-gas flowing through the oxidizing gas flow path 2a and discharged to the discharge path 12 flows to the discharge side connection portion C through the pressure regulating valve 16 and the like. Therefore, in the discharge side connection portion C, the bypass air and the oxidizing off gas merge.

  Here, if the bypass air passes through the pressure loss body, the sound produced by the bypass air (for example, sound such as pulsation sound from the compressor 14) is muted to some extent as a result. However, since the bypass air flows to the discharge side connection portion C without passing through the pressure loss body such as the humidifier 15, there is a possibility that the sound becomes very loud due to the merge of the bypass air and the oxidizing off gas. Therefore, in this embodiment, the piping structure is such that no loud noise is generated while the bypass valve 18 is open.

  That is, in the piping structure of the present embodiment, the length of at least one of the supply path 11, the discharge path 12 and the bypass path 17 is adjusted, and the bypass air and the oxidant off-gas that are out of phase with each other are discharged from the discharge side connection portion C. It has come to join.

Specifically, the phase of the sound wave f ₁ that the bypass air brings to the discharge side connection portion C (in other words, the sound wave that is brought from the bypass passage 17 to the discharge side connection portion C while the bypass valve 18 is opened) and the oxidation The phase of the sound wave f ₂ that the off gas brings to the discharge side connection portion C (in other words, the sound wave that is brought from the discharge passage 12 to the discharge side connection portion C while the bypass valve 18 is open) is shifted from each other. Preferably, both are completely opposite (reverse phase). By doing so, the sound brought about by the bypass air and the sound brought about by the oxidation off gas are attenuated so as to cancel each other, so that it is possible to suppress the generation of a loud sound due to the merging of the oxidation gas and the oxidation off gas.

Here, it is assumed that the sound produced by the bypass air is a dull sound (frequency is constant) and the sound produced by the oxidizing off gas is a dull sound, and both have a constant wavelength λ. In this case, in order to make the sound wave f ₁ and the sound wave f ₂ have opposite phases, for example, any one of the following pipe structures (10) to (15) may be used. Of course, the present invention is not limited to these.
L ₁ −M ₁ ≈λ / 2 (10)
L ₁ −M ₂ ≈λ / 2 (11)
L ₁ −M ₃ ≈λ / 2 (12)
L ₂ −M ₁ ≈λ / 2 (13)
L ₂ −M ₂ ≈λ / 2 (14)
L ₂ −M ₃ ≈λ / 2 (15)

Here, L ₁ is the piping length of the supply path 11 and the bypass path 17 in the part from the discharge port of the compressor 14 via the supply side connection part B to the discharge side connection part C. L ₂ is the pipe length of the bypass passage 17 in the portion from the outlet of the bypass valve 18 to the discharge side connection portion C. M ₁ is the pipe length of the discharge path 12 in the portion from the cathode outlet (upstream end of the discharge path 12) of the fuel cell 2 to the discharge side connection C. M ₂ is the pipe length of the discharge passage 12 at the portion from the outlet of the back pressure regulating valve 16 to the discharge side connection portion C. M ₃ is the pipe length of the discharge path 12 in the portion from the outlet of the humidifier 15 to the discharge side connection portion C.

  As described above, according to the fuel cell system 1 of the present embodiment, the hydrogen concentration in the oxidizing off gas can be reduced by the bypass air even during the low-efficiency operation, and the generation of a loud sound accompanying the merging of the bypass air and the oxidizing off gas is generated. Can be suppressed. Therefore, the noise reduction effect while the bypass valve 18 is opened can be enhanced with a simple piping structure.

Second Embodiment
Next, the fuel cell system 1 according to the second embodiment will be briefly described focusing on the differences. The difference from the first embodiment is that generation of a loud sound accompanying the merging of the bypass air and the oxidizing off gas is suppressed by a method other than the piping structure.

  Specifically, the bypass valve 18 of the present embodiment is configured by a variable valve that can adjust the valve opening. For example, a butterfly valve can be used as the variable valve. In addition, the valve opening degree can also be restated as an opening area between the valve body and the valve seat. The bypass valve 18 is connected to the control device 7, and is configured so that the control device 7 can switch the valve opening degree in a multistage, continuous (stepless) or linear manner.

  Depending on the valve opening degree of the bypass valve 18, resonance may occur due to the merge of the bypass air and the oxidizing off gas while the bypass valve 18 is opened. Due to this resonance, a loud noise is generated in the oxidizing gas piping system 3. Therefore, in order to avoid such a situation, in this embodiment, the control device 7 opens and closes the bypass valve 18 so that resonance does not occur due to the merge of the bypass air and the oxidizing off gas while the bypass valve 18 is opened. I try to control it. In order to open and close the bypass valve 18 so that resonance does not occur, the valve opening at which the resonance occurs may be skipped instantaneously, that is, the valve opening may not be stopped for a certain period of time. . It should be noted that the valve opening at which resonance occurs is obtained in advance and stored in the ROM of the control device 7.

  As described above, according to the present embodiment, since the bypass valve 18 is controlled to open and close in consideration of resonance, the generation of a loud sound due to the merge of the bypass air and the oxidizing off gas is suppressed as in the first embodiment. it can.

<Modification>
In each of the above-described embodiments, the case where the low-efficiency operation is performed at the time of starting the system is illustrated. However, the low-efficiency operation may be performed when the system required power becomes a predetermined value or less or when there is a system stop instruction, for example. .

  Alternatively, a variable valve may be separately provided in the bypass passage 17, and the phase of the sound waves of the bypass air and the oxidizing off gas may be shifted by adjusting the variable valve. Further, a general expansion type or resonance type silencer may be provided on the bypass passage 17 downstream of the bypass valve 18 so as to reduce the noise caused by the bypass air.

It is a block diagram of the fuel cell system which concerns on this embodiment. It is a graph which shows the relationship between FC electric current and FC voltage concerning this embodiment. It is a figure for demonstrating the generation | occurrence | production mechanism of the pumping hydrogen which concerns on this embodiment, (A) shows the battery reaction at the time of normal operation, (B) shows the battery reaction at the time of low efficiency operation. It is a block diagram which expands and shows the oxidizing gas piping system which concerns on this embodiment.

Explanation of symbols

  1: fuel cell system, 2: fuel cell, 7: control device, 11: supply path, 12: discharge path, 14: compressor (supply machine), 15: humidifier, 16: back pressure regulating valve (pressure regulating valve), 17: Bypass path, 18: Bypass valve, B: Supply side connection, C: Discharge side connection

Claims (10)

A supply path through which oxidizing gas supplied to the fuel cell flows;
A feeder that is provided in the supply path and pumps the oxidizing gas to the fuel cell;
An exhaust path through which the oxidizing off-gas exhausted from the fuel cell flows;
A bypass path connecting the supply path and the discharge path so that the oxidizing gas flows bypassing the fuel cell;
In a fuel cell system comprising a bypass valve for opening and closing the bypass path,
At least one of the supply path, the discharge path, and the bypass path is adjusted in pipe length so that the oxidant gas and the oxidant off-gas that are out of phase with each other are merged during the opening of the bypass valve. , Fuel cell system.   The fuel cell system according to claim 1, further comprising a control device that controls opening and closing of the bypass valve. A supply path through which oxidizing gas supplied to the fuel cell flows;
A feeder that is provided in the supply path and pumps the oxidizing gas to the fuel cell;
An exhaust path through which the oxidizing off-gas exhausted from the fuel cell flows;
A bypass path connecting the supply path and the discharge path so that the oxidizing gas flows bypassing the fuel cell;
In a fuel cell system comprising a bypass valve for opening and closing the bypass path,
A fuel cell system comprising a control device that controls opening and closing of the bypass valve so that resonance does not occur due to the merging of the oxidizing gas and the oxidizing off gas during the opening of the bypass valve.   The fuel according to claim 3, wherein the control device controls the opening and closing of the bypass valve so as to skip a valve opening degree at which resonance occurs due to the merging of the oxidizing gas and the oxidizing off gas while the bypass valve is opened. Battery system.   5. The fuel cell according to claim 2, wherein the control device closes the bypass valve when the fuel cell system is in operation and opens the bypass valve when the fuel cell system is activated. 6. system.   The fuel cell system according to claim 5, wherein the control device opens the bypass valve only when the fuel cell system is activated and at a predetermined low temperature.   The fuel cell according to any one of claims 2 to 4, wherein the control device opens the bypass valve when performing a low-efficiency operation with a large power loss as compared with a normal operation of the fuel cell system. system.   The fuel cell system according to claim 7, wherein the low efficiency operation is performed only at a predetermined low temperature. A humidifier that is provided in the supply path downstream of the supply machine and humidifies the oxidizing gas;
The fuel cell system according to any one of claims 1 to 8, wherein a supply side connection portion between the supply path and the bypass path is located upstream of the humidifier.   The fuel cell system according to any one of claims 1 to 9, further comprising a pressure regulating valve provided in the discharge path.

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