JP5835151B2 - Fuel cell system - Google Patents

Description

  The present invention relates to fuel cell technology.

  As a method for controlling the output of the fuel cell, a technique for controlling the supply pressure of cathode gas supplied to the fuel cell is known (Patent Document 1 below). The fuel cell has a characteristic that the output increases when the supply pressure of the cathode gas is increased. In the following Patent Document 1, the back pressure of the cathode off gas discharged from the fuel cell is increased by controlling the back pressure valve in the closing direction, and as a result, the cathode gas supply pressure is increased to increase the output of the fuel cell. The technology is described.

Japanese Unexamined Patent Publication No. 2009-004160

  However, when the supply pressure of the cathode gas is increased by back pressure control, the cathode gas that has become hot as the pressure increases is supplied to the fuel cell, and the electrolyte membrane included in the fuel cell dries, resulting in a decrease in output performance or electrolyte. It has been pointed out that there is a risk of film deterioration. In addition, even when the cathode gas is cooled by a cooling device such as an intercooler just before being supplied to the fuel cell, if the cathode gas suddenly becomes high due to an increase in back pressure, it is cooled by the cooling device. Previously, the problem of cathode gas being supplied to the fuel cell was also pointed out.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.
(1) A first aspect of the present invention is a fuel cell system, which is a fuel cell, a gas supply unit that supplies cathode gas, and a supply flow that distributes the cathode gas from the gas supply unit to the fuel cell. A discharge passage for flowing a cathode off gas discharged from the fuel cell, a back pressure adjusting unit for adjusting a back pressure of the cathode off gas, and the discharge flow from the gas supply unit without passing through the fuel cell. A bypass channel for circulating the cathode gas in the channel, and a cathode gas supplied from the gas supply unit so that the cathode channel supplied to either the supply channel or the bypass channel The back pressure is controlled by a switching unit that performs switching, a temperature detection unit that detects the temperature of the cathode gas supplied from the gas supply unit, and the back pressure adjustment unit, A fuel cell system comprising: a control unit that controls the switching unit so that the cathode gas flows through the bypass channel when the temperature detection unit detects that the temperature of the cathode gas exceeds a predetermined temperature. Offered as.
( 2 ) According to the second aspect of the present invention, a fuel cell system is provided. The fuel cell system includes: a fuel cell; a gas supply unit that supplies a cathode gas; a supply channel that distributes the cathode gas from the gas supply unit to the fuel cell; and a cathode off-gas that is discharged from the fuel cell. A discharge flow path for flowing; a back pressure adjusting section for adjusting a back pressure of the cathode off gas; a bypass flow path for flowing the cathode gas from the gas supply section to the discharge flow path without passing through the fuel cell; A switching unit that switches between the two flow paths so that the cathode gas supplied from the gas supply part flows through either the supply flow path or the bypass flow path; and supplied from the gas supply part A temperature detecting unit for detecting the temperature of the cathode gas generated; the back pressure adjusting unit increases the back pressure; and the temperature detecting unit sets the temperature of the cathode gas to a predetermined temperature. When it is detected that exceeds the said cathode gas to the bypass passage and a control section for controlling the switching unit so as to flow; comprises. According to the fuel cell system of this embodiment, when the cathode gas rises above a predetermined temperature by increasing the back pressure, the fuel cell is bypassed and the cathode gas is circulated. Accordingly, it is possible to avoid supplying a high-temperature cathode gas to the fuel cell.

  Note that the present invention can be realized in various modes. For example, it can be realized in the form of a fuel cell, a fuel cell driving method, a fuel cell vehicle, a fuel cell vehicle control method, and the like.

1 is an explanatory diagram illustrating a configuration of a fuel cell system 10. FIG. It is a flowchart which shows the flow of a cathode gas supply process. It is a graph which shows the relationship between back pressure and inlet gas temperature.

A. First embodiment:
(A1) Configuration of fuel cell:
FIG. 1 is an explanatory diagram illustrating the configuration of a fuel cell system 10 as a first embodiment of the present invention. The fuel cell system 10 is a power supply system that is mounted on a fuel cell vehicle (hereinafter also simply referred to as a vehicle) that travels using power generated by the fuel cell as a power source. In addition, the fuel cell system 10 may be applied as a household or commercial power generation system. In this description, the gas supply system in the fuel cell system 10 will be mainly described, and in particular, the description will focus on the cathode gas supply system.

  The fuel cell system 10 includes a fuel cell 20, a cathode gas supply system 30, an anode gas supply system 50, a cooling system 60, and a control unit 70. The fuel cell 20 is a solid polymer fuel cell that generates electric power through an electrochemical reaction between an oxidizing gas (cathode gas) and a fuel gas (anode gas). The fuel cell 20 has a stack structure in which a plurality of fuel cell single cells in which catalyst electrodes and separators are laminated on both sides of an electrolyte membrane are laminated in a predetermined direction. In the present embodiment, the cathode gas is air and the anode gas is hydrogen gas.

  The cathode gas supply system 30 is a gas supply system that supplies cathode gas (air) to the fuel cell 20. The cathode gas supply system 30 includes pipes 32, 33, and 36, a first switching pipe 34, and a second switching pipe 35 as pipes through which gas flows. Further, the cathode gas supply system 30 is a device for controlling the gas flowing through the pipe, as a compressor 41, a flow sensor 42, an intercooler 43, a temperature sensor 44, a three-way valve 45, and a pressure sensor 46. The back pressure valve 47 is provided. As shown in the figure, the operation of these devices (the compressor 41 to the back pressure valve 47) is controlled by the control unit 70. In addition, the control unit 70 controls the output of the fuel cell 20 by monitoring the output generated by the power generation of the fuel cell 20 and controlling each device included in the cathode gas supply system 30.

  The pipe 32 is a pipe that communicates the outside with the compressor 41. The compressor 41 takes in the cathode gas (air) from the outside through the pipe 32, compresses it, and supplies it to the pipe 33. The flow rate sensor 42 measures the flow rate of the cathode gas supplied to the pipe 33 by the compressor 41. The control unit 70 acquires the value of the flow rate from the flow sensor 42 and controls the flow rate of the cathode gas supplied from the compressor 41 to the pipe 33 by feedback control.

  The pipe 33 is connected to the three-way valve 45 via the intercooler 43. The intercooler 43 cools the cathode gas flowing through the pipe 33. The cooling water supplied from the cooling system 60 circulates inside the intercooler 43, and the intercooler 43 cools the cathode gas flowing through the pipe 33 with this cooling water. Also. A temperature sensor 44 is installed in the pipe 33 and measures the temperature of the cathode gas flowing through the pipe 33 (hereinafter also referred to as inlet gas temperature). The controller 70 acquires the value of the inlet gas temperature from the temperature sensor 44 and controls the intercooler 43 by feedback control. With such control, the control unit 70 controls the gas temperature of the cathode gas flowing through the pipe 33.

  The three-way valve 45 is a switching valve that allows the cathode gas flowing through the pipe 33 to flow through either the first switching pipe 34 or the second switching pipe 35. The switching operation of the three-way valve 45 is performed by the control unit 70 by a cathode gas supply process described later. The first switching pipe 34 is a pipe that supplies the cathode gas to the fuel cell 20. The cathode gas supplied to the fuel cell 20 via the first switching pipe 34 is used for power generation by an electrochemical reaction with the anode gas supplied to the fuel cell 20 by the anode gas supply system 50, and the pipe 36 serves as a cathode offgas. Then, it is discharged to the outside through the back pressure valve 47. On the other hand, the second switching pipe 35 is a pipe that bypasses the fuel cell 20 and is connected to the pipe 36. The cathode gas flowing through the second switching pipe 35 is discharged to the outside through the pipe 36 and the back pressure valve 47.

  A pressure sensor 46 installed in the pipe 36 measures the back pressure of the cathode off gas flowing through the pipe 36. The back pressure valve 47 is an adjustment valve that adjusts the back pressure according to the opening of the valve. The controller 70 controls the back pressure by adjusting the opening of the back pressure valve 47 based on the back pressure value acquired from the pressure sensor 46. In general, it is known as a characteristic of a fuel cell that the power generation performance increases when the supply pressure of the cathode gas is increased. For example, when the required output to the fuel cell is high, the supply pressure of the cathode gas is increased and the output from the fuel cell is increased by controlling the back pressure valve 47 in the closing direction (hereinafter also referred to as closing control). be able to. Since the technique for controlling the output of the fuel cell by back pressure control is a known technique (for example, Patent Document 1), description thereof is omitted.

  The anode gas supply system 50 is a gas supply system for supplying anode gas to the fuel cell 20. The anode gas supply system 50 includes a hydrogen tank 51 and pipes 52 and 53. The anode gas (hydrogen gas) in the hydrogen tank 51 is supplied to the fuel cell 20 via the pipe 52. The anode gas supplied to the fuel cell 20 is supplied to the power generation by an electrochemical reaction with the cathode gas supplied to the fuel cell 20 by the cathode gas supply system 30 and is discharged to the outside through the pipe 53 as an anode off gas. . In addition, the anode gas supply system 50 has a gas distribution system (not shown) for reusing hydrogen gas contained in the anode off gas as the anode gas.

  The cooling system 60 is a system for circulating and cooling cooling water through the fuel cell 20 and the intercooler 43. The cooling system 60 includes pipes 61 to 64, a pump 65, a radiator 66, a rotary valve 67, and a temperature sensor 68. Cooling water flows through the pipes 61 to 64. The pump 65 applies pressure to the cooling water and circulates the cooling water through each pipe. The pipe 61 communicates with the inside of the fuel cell 20, and the cooling water circulating through the pipe 61 cools the fuel cell 20. The pipes 63 and 64 are pipes for circulating cooling water through the intercooler 43.

  The radiator 66 cools the cooling water whose temperature has increased due to the cooling of the fuel cell 20 and the intercooler 43. The cooling water cooled by the radiator 66 is circulated through the pipes 61 to 64 again. The rotary valve 67 adjusts the circulation flow rate of the cooling water to the fuel cell 20 and the intercooler 43 according to the opening degree. The opening degree of the rotary valve 67 is controlled by the control unit 70. The temperature sensor 68 measures the temperature of the cooling water flowing through the pipe 61. The control unit 70 manages the temperature of the cooling water based on the temperature acquired from the temperature sensor 68. With the configuration described above, the fuel cell system 10 generates power.

(A2) Cathode gas supply process:
Next, the cathode gas supply process performed by the control unit 70 will be described. The cathode gas supply process is a process in which the control unit 70 controls the cathode gas supplied to the fuel cell 20 by controlling each device provided in the cathode gas supply system 30. FIG. 2 is a flowchart for explaining the flow of the cathode gas supply process. When a vehicle power switch (not shown) is turned on by a driver's operation, the control unit 70 starts a cathode gas supply process. When starting the cathode gas supply process, the controller 70 operates the compressor 41 to supply the cathode gas to the fuel cell 20 (step S102). At this time, the control unit 70 controls the three-way valve 45 and supplies the cathode gas to the fuel cell 20 using the first switching pipe 34 as an initial state.

  After starting the supply of the cathode gas, the control unit 70 performs back pressure control for controlling the opening degree of the back pressure valve 47 in accordance with the amount of power required as the power source of the vehicle (step S104). Specifically, the opening of the back pressure valve 47 is controlled according to the accelerator depression amount by the driver of the vehicle, and the output of the fuel cell 20 is controlled. When the output of the fuel cell 20 is increased, the control unit 70 closes the back pressure valve 47 to increase the back pressure (hereinafter also referred to as back pressure increase control). On the contrary, when the output of the fuel cell 20 is lowered, the back pressure valve 47 is controlled to be opened to lower the back pressure.

  After starting the back pressure control, the control unit 70 acquires the value of the inlet gas temperature from the temperature sensor 44. The control unit 70 controls the three-way valve 45 according to the value of the inlet gas temperature and supplies the cathode gas to the fuel cell 20 via the first switching pipe 34 or bypasses the fuel cell 20 via the second switching pipe 35. Judge whether to distribute cathode gas. Specifically, when the acquired inlet gas temperature is equal to or lower than the predetermined value α (step S106: NO), the control unit 70 controls the three-way valve 45 to the fuel cell 20 via the first switching pipe 34. Cathode gas is supplied (step S108). In the case of this embodiment, since the three-way valve 45 is controlled so as to use the first switching pipe 34 as an initial state (see step S102), when it is determined that the first switching pipe 34 supplies the three-way valve 45, The actual operation of is not accompanied.

  On the other hand, when the inlet gas temperature is higher than the predetermined value α (step S106: YES), the control unit 70 causes the three-way valve 45 to bypass the fuel cell 20 through the second switching pipe 35 and distribute the cathode gas ( Step S110). The control unit 70 repeats the processes in steps S102 to S110 until the power switch of the vehicle is turned off (step S112). In this way, the control unit 70 performs the cathode gas supply process. Note that during the period in which the second switching pipe 35 bypasses the fuel cell 20 to circulate the cathode gas, the electric power necessary for the vehicle is supplied from a battery (not shown) provided separately in the vehicle.

  Next, the cathode gas supply process in this embodiment will be described with reference to a graph. FIG. 3 is a graph showing the relationship between the back pressure and the inlet gas temperature when the cathode gas supply process is performed. The horizontal axis of the graph represents time. The illustrated “CA back pressure” indicates the back pressure of the cathode off gas. The CA back pressure is a pressure value measured by the pressure sensor 46. The inlet gas temperature is a value measured by the temperature sensor 44.

  As described above, in the initial state where the control unit 70 starts the cathode gas supply process, the cathode gas is supplied to the fuel cell 20 through the first switching pipe 34. When the control unit 70 starts back pressure increase control in order to increase the output of the fuel cell 20, the back pressure increases. When the back pressure increases, the supply pressure of the cathode gas flowing through the pipe 33 also increases. The temperature of the cathode gas increases as the pressure increases.

  The controller 70 detects an increase in the inlet gas temperature by the temperature sensor 44 and controls the intercooler 43 to cool the cathode gas. At this time, when the cooling response by the intercooler 43 is slow with respect to the temperature rise of the cathode gas, the cathode gas inlet gas temperature rises rapidly. When the temperature sensor 44 detects that the inlet gas temperature has exceeded α, the control unit 70 controls the three-way valve 45 and bypasses the fuel cell 20 by the second switching pipe 35 to allow the cathode gas to flow. .

  Thereafter, when the cathode gas is stably cooled by the intercooler 43, the temperature of the cathode gas decreases. When the temperature sensor 44 detects that the inlet gas temperature has become less than or equal to α, the control unit 70 controls the three-way valve 45 and supplies the cathode gas to the fuel cell 20 through the first switching pipe 34.

  As described above, the fuel cell system 10 changes the cathode gas flow path from the first switching pipe 34 to the first switching pipe 34 when the inlet gas temperature of the cathode gas exceeds α by back pressure increase control in the cathode gas supply process. Switch to 2 switching pipe 35. Then, the fuel cell 20 is bypassed and the cathode gas is circulated. Accordingly, it is possible to avoid supplying the fuel cell 20 with the cathode gas that has been temporarily brought to a high temperature by the back pressure increase control. As a result, it is possible to suppress deterioration and performance deterioration of the fuel cell.

B. Variation:
The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
(B1) Modification 1:
In the above-described embodiment, the switching between the first switching pipe 34 and the second switching pipe 35 is performed using one three-way valve. However, the present invention is not limited to this, for example, the second switching pipe 35 and the pipe 36. A three-way valve may be further provided in the connecting portion. Also, the check valves may be switched using two. Even if it does in this way, the effect similar to the said embodiment can be acquired.

(B2) Modification 2:
In the above embodiment, the back pressure valve 47 is employed as the back pressure adjusting unit. However, the back pressure may be controlled by other methods without being limited thereto. For example, a pipe that can adjust the cross-sectional area of the flow path may be adopted as a part of the pipe 36. In addition, the back pressure may be controlled by adopting a plurality of pipes having different channel cross-sectional areas as a part of the pipe 36 and switching the pipes to circulate the cathode off gas.

(B3) Modification 3:
In the above embodiment, the inlet gas temperature is actually measured by the temperature sensor 44 and it is detected whether or not it exceeds the predetermined value α. However, the present invention is not limited to this, and the inlet gas temperature is started when the back pressure increase control is started. May be estimated, and the three-way valve 45 may be controlled so that the cathode gas flows through the second switching pipe 35. In addition, the three-way valve 45 may be controlled after a predetermined time has elapsed from the start of the back pressure increase control so that the cathode gas flows through the second switching pipe 35.

(B4) Modification 4:
In the above-described embodiment, the cathode gas is controlled to flow through only one of the first switching pipe 34 and the second switching pipe 35 by the three-way valve 45. However, the present invention is not limited to this. The three-way valve 45 may be controlled so that 80% of the cathode gas flowing through the pipe 33 flows through the second switching pipe 35 and 20% flows through the first switching pipe 34 when α exceeds. That is, when the inlet gas temperature exceeds α, the three-way valve 45 may be controlled so that at least a part of the cathode gas flowing through the pipe 33 flows through the second switching pipe 35.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 20 ... Fuel cell 30 ... Cathode gas supply system 32, 33, 36, 37, 52, 53, 61, 63 ... Piping 34 ... 1st switching piping 35 ... 2nd switching piping 41 ... Compressor 42 ... Flow volume Sensor 43 ... Intercooler 44 ... Temperature sensor 45 ... Three-way valve 46 ... Pressure sensor 47 ... Back pressure valve 50 ... Anode gas supply system 51 ... Hydrogen tank 60 ... Cooling system 65 ... Pump 66 ... Radiator 67 ... Rotary valve 68 ... Temperature sensor 70 ... Control unit

Claims (2)

A fuel cell system,
A fuel cell;
A gas supply unit for supplying cathode gas;
A supply flow path for flowing the cathode gas from the gas supply unit to the fuel cell;
A discharge flow path for circulating a cathode off-gas discharged from the fuel cell;
A back pressure adjusting unit for adjusting the back pressure of the cathode off gas;
A bypass flow path for allowing the cathode gas to flow from the gas supply section to the discharge flow path without passing through the fuel cell;
A switching unit that switches between the two flow paths so that the cathode gas supplied from the gas supply unit flows into either the supply flow path or the bypass flow path;
A temperature detection unit for detecting the temperature of the cathode gas supplied from the gas supply unit;
The back pressure is controlled by the back pressure adjusting unit, and when the temperature detecting unit detects that the temperature of the cathode gas exceeds a predetermined temperature, the cathode gas flows through the bypass flow path. A fuel cell system comprising: a control unit that controls the switching unit.   The fuel cell system according to claim 1, wherein
  The controller is
    Back pressure control for increasing the back pressure when the required power for the fuel cell increases, and for reducing the back pressure when the required power for the fuel cell decreases;
    Channel switching for controlling the switching unit so that the cathode gas flows through the bypass channel when it is detected that the temperature of the cathode gas exceeds the predetermined temperature after increasing the back pressure Control,
  Run the fuel cell system.

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