Fuel cell system

Abstract

To provide a fuel battery system capable of warming a secondary battery while suppressing deterioration of a secondary battery.SOLUTION: A warming device 60 of a fuel battery system, comprises: a warming flow channel 61 that is branched from a second supply path 31c, and is extended to a secondary battery 12 so as to be adjacent; a flow channel control valve 33 that enables a flow of air after thermal conversion from the second supply path 31c to the warming flow channel 61; and a control device 70 that controls an operation of the flow channel control valve 33. The control device 70 is discharged from the secondary battery 12 to an air compressor 32 and switches the flow channel control valve 33 for flowing the air after thermal conversion by an inter cooler 25 to the warming flow channel 61 in the case where a temperature of the secondary battery 12 becomes smaller than a preset threshold value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005]

[0001] The present invention relates to a fuel cell system.

Background Art

[0002] Some fuel cell systems equipped with a fuel cell stack include a secondary battery. The secondary battery is, for example, a power source for a pump that supplies air to the fuel cell stack. Since the charge-discharge performance of the secondary battery deteriorates when the temperature decreases, the secondary battery is warmed up. Patent Document 1 discloses a warming device for a fuel cell system that warms up the secondary battery with a heater. In the warming device disclosed in Patent Document 1, the heat of the heater heated by the power supply from the secondary battery is transferred to the secondary battery, thereby warming up the secondary battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in warming up the secondary battery using a heater, the more current flowing from the secondary battery to the heater, the shorter the warming-up time by the heater can be. However, the more current flowing through the heater, the higher the temperature of the heater becomes excessively. Then, the secondary battery deteriorates, which is not preferable. [[ID=************]]

Means for Solving the Problems

[0005] <*********A fuel cell system for solving the above problems comprises a secondary battery that serves as a power source for an auxiliary device, a fuel cell stack, an air compressor that pressurizes and pumps air to the fuel cell stack, an intercooler that exchanges heat with a heat transfer medium before supplying the air discharged from the air compressor to the fuel cell stack, and a supply path for supplying the air after heat exchange in the intercooler to the fuel cell stack, wherein the fuel cell system comprises a warm-up passage branching off from the supply path and extending adjacent to the secondary battery, a switching valve that allows the air after heat exchange to flow from the supply path to the warm-up passage, and a control device that controls the operation of the switching valve, wherein the control device, when the temperature of the secondary battery falls below a preset threshold, discharges the secondary battery using the air compressor as an auxiliary device, and switches the switching valve so that the air discharged from the air compressor driven by the discharge and after heat exchange in the intercooler flows into the warm-up passage.

[0006] According to this, the secondary battery is warmed up by internal warming, which is performed by discharge from the secondary battery to the air compressor, and external warming, which is performed using air that has flowed through the warming passage. External warming is performed using air that has undergone heat exchange in the intercooler. Since the air that has undergone heat exchange in the intercooler is the air supplied to the fuel cell stack, it does not become excessively hot. Therefore, unlike when a heater is used, heating by external warming does not occur at excessively high temperatures. This suppresses the deterioration of the secondary battery due to excessive heat. As a result, the secondary battery can be suitably warmed up by both internal and external warming while suppressing the deterioration of the secondary battery.

[0007] The fuel cell system may be equipped with a diluent into which hydrogen gas discharged from the anode of the fuel cell stack flows, and air flowing through the warming channel may be supplied to the diluent.

[0008] According to this, the air used for external warming of secondary batteries can be used to dilute hydrogen gas. The fuel cell system includes a cooling water circuit for supplying cooling water to the fuel cell stack and for discharging the cooling water from the fuel cell stack, the cooling water circuit including a cooling water pump for pressurizing the cooling water, and the cooling water pump may be powered by the secondary battery.

[0009] According to this, since the secondary battery discharges not only to the air compressor but also to the cooling water pump, the Joule heating due to the internal resistance of the secondary battery is greater compared to when it discharges only to the air compressor. As a result, the temperature of the secondary battery can be raised compared to when it discharges only to the air compressor, which enhances the internal warming function of the secondary battery and allows for faster warming of the secondary battery.

[0010] The fuel cell system may be equipped with an auxiliary heater to assist in warming up the secondary battery. According to this, the auxiliary heater can assist in warming up the secondary battery, allowing it to warm up more quickly. [Effects of the Invention]

[0011] This invention allows for the warming up of a secondary battery while suppressing its degradation. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram showing a fuel cell system. [Figure 2] Figure 2 is a schematic perspective view showing the secondary battery and the warming-up channel. [Figure 3] Figure 3 is a schematic diagram showing the flow control valve when it is switched to the first position. [Figure 4] Figure 4 is a schematic diagram showing the state when the flow control valve is switched to the second position. [Figure 5] Figure 5 is a schematic diagram showing an example of a fuel cell system. [Modes for carrying out the invention]

[0013] Hereinafter, an embodiment of a fuel cell system will be described with reference to FIGS. 1 to 4. <Fuel cell system> As shown in FIG. 1, the fuel cell system 10 includes a fuel cell stack 11, a cooling water circuit 20, an air supply circuit 30, a hydrogen gas circuit 40, an air discharge circuit 50, a warm-up device 60, a secondary battery 12, and a control device 70.

[0014] <Fuel cell stack> The fuel cell stack 11 includes a plurality of fuel cells. Each of the plurality of fuel cells is a polymer membrane type fuel cell in which a cathode electrode, an anode electrode, and an electrolyte membrane disposed between both electrodes are laminated. The fuel cells of the fuel cell stack 11 generate electricity by a chemical reaction between oxygen and hydrogen in the air.

[0015] <Cooling water circuit> The cooling water circuit 20 supplies cooling water to the fuel cell stack 11 and discharges the cooling water from the fuel cell stack 11. The cooling water circuit 20 includes a cooling water circulation flow path 21, a radiator 23, a cooling water pump 24, and an intercooler 25.

[0016] Cooling water for cooling the fuel cell stack 11 flows through the cooling water circulation flow path 21. In the cooling water circulation flow path 21, the direction in which the cooling water flows is referred to as the "flow direction". The upstream end and the downstream end in the flow direction in the cooling water circulation flow path 21 are connected to the fuel cell stack 11.

[0017] The radiator 23 forms a part of the cooling water circulation flow path 21. The radiator 23 exchanges heat between the cooling water flowing through the cooling water circulation flow path 21 and the outside air. Therefore, the cooling water heat-exchanged with the fuel cell stack 11 is cooled by heat exchange with the outside air in the radiator 23.

[0018] The cooling water pump 24 is provided on the downstream side of the radiator 23 and on the upstream side of the intercooler 25 in the flow direction in the cooling water circulation passage 21. The cooling water pump 24 pumps the cooling water to circulate the cooling water in the cooling water circulation passage 21. The motor M1 that drives the cooling water pump 24 is electrically connected to the inverter 13. The inverter 13 converts the DC power discharged from the secondary battery 12 into AC power and supplies it to the motor M1. When the motor M1 is driven by driving the inverter 13, the cooling water pump 24 is driven. Therefore, the cooling water pump 24 is powered by the secondary battery 12.

[0019] The intercooler 25 is provided on the downstream side of the cooling water pump 24 and on the upstream side of the fuel cell stack 11 in the flow direction in the cooling water circulation passage 21. The intercooler 25 forms a part of the cooling water circulation passage 21. The intercooler 25 exchanges heat between the cooling water as the heat medium flowing through the cooling water circulation passage 21 and the air discharged from the air compressor 32 described later.

[0020] <Air supply circuit> The air supply circuit 30 supplies air to the fuel cell stack 11. The air supply circuit 30 includes an air supply passage 31, an air compressor 32, and a flow path control valve 33 as a switching valve.

[0021] Air for supplying the fuel cell stack 11 flows through the air supply passage 31. In the air supply passage 31, the direction of air flow is described as the "flow direction". The downstream end portion in the flow direction in the air supply passage 31 is connected to the fuel cell stack 11. The upstream end portion in the flow direction in the air supply passage 31 is open to the atmosphere via the intake filter F.

[0022] The air compressor 32 is located downstream of the intake filter F in the flow direction of the air supply passage 31. The air compressor 32 is equipped with a motor M2. The motor M2 is electrically connected to the inverter 14. The inverter 14 converts the DC power discharged from the secondary battery 12 into AC power and supplies it to the motor M2. When the motor M2 is driven by the inverter 14, the air compressor 32 is driven. The air compressor 32 compresses the air drawn in through the intake filter F and the air supply passage 31 and discharges it into the air supply passage 31, and also pumps air to the fuel cell stack 11.

[0023] A portion of the air supply passage 31 passes through the intercooler 25. The flow control valve 33 is located downstream of the intercooler 25 in the flow direction of the air supply passage 31. The flow control valve 33 controls the direction of air flow through the air supply passage 31. The flow control valve 33 will be described in detail later.

[0024] The air supply passage 31 comprises a first supply passage 31a, a cooling passage 31b, and a second supply passage 31c. The first supply passage 31a connects the discharge port 32a of the air compressor 32 to the inlet 25a of the intercooler 25. Air heated to a high temperature by being pumped by the air compressor 32 flows through the first supply passage 31a. In the following description, the air heated to a high temperature by being pumped by the air compressor 32 will be referred to as "high-temperature air." The temperature of the high-temperature air is higher than the temperature suitable for power generation by the fuel cell stack 11.

[0025] The cooling passage 31b connects the inlet 25a and the outlet 25b of the intercooler 25. The cooling passage 31b is located inside the intercooler 25. Therefore, the cooling passage 31b of the air supply passage 31 is part of the air supply passage 31 that passes through the intercooler 25.

[0026] High-temperature air discharged from the air compressor 32 flows through the cooling channel 31b. In the intercooler 25, heat exchange takes place between the cooling water flowing through the cooling water circulation channel 21 and the high-temperature air flowing through the cooling channel 31b. As a result, the high-temperature air is cooled. Therefore, the intercooler 25 causes the air discharged from the air compressor 32 to exchange heat with the cooling water before being supplied to the fuel cell stack 11. The air whose temperature has decreased from that of the high-temperature air due to the heat exchange in the intercooler 25 is referred to as "temperature-controlled air". The temperature of the temperature-controlled air is within the temperature range suitable for power generation by the fuel cell stack 11. Therefore, the intercooler 25 cools the high-temperature air to a temperature range suitable for power generation by heat exchange with the high-temperature air.

[0027] The second supply passage 31c connects the outlet 25b of the intercooler 25 to the fuel cell stack 11. The temperature-controlled air flowing into the second supply passage 31c is supplied to the cathode electrode of the fuel cell stack 11. Therefore, the second supply passage 31c is a supply passage for supplying air that has undergone heat exchange in the intercooler 25 to the fuel cell stack 11. A flow control valve 33 is also provided in the second supply passage 31c. As a result, the temperature-controlled air flowing into the second supply passage 31c flows into the flow control valve 33.

[0028] <Hydrogen gas circuit> The hydrogen gas circuit 40 supplies hydrogen gas to the fuel cell stack 11 and discharges hydrogen gas from the fuel cell stack 11. The hydrogen gas circuit 40 comprises a hydrogen gas supply channel 41, an injector 42, a hydrogen gas circulation channel 46, a gas-liquid separator 47, and a hydrogen circulation pump 48.

[0029] Hydrogen gas supplied to the fuel cell stack 11 flows through the hydrogen gas supply channel 41. In the hydrogen gas supply channel 41, the direction in which the hydrogen gas flows is referred to as the "flow direction." The downstream end of the hydrogen gas supply channel 41 in the flow direction is connected to the fuel cell stack 11.

[0030] The injector 42 is located on the upstream end side in the flow direction of the hydrogen gas supply channel 41. The injector 42 is, for example, an electromagnetically driven on-off valve in which the valve body is driven electromagnetically. The injector 42 adjusts the flow rate of hydrogen gas supplied from a hydrogen tank (not shown) to the fuel cell stack 11.

[0031] The hydrogen gas circulation channel 46 is connected to the fuel cell stack 11 and to the section of the hydrogen gas supply channel 41 downstream of the injector 42. From the anode of the fuel cell stack 11, anode off gas is discharged, which contains hydrogen gas that did not react in the fuel cell stack 11, water produced by the chemical reaction between hydrogen gas and oxygen, and impurities such as nitrogen. The anode off gas discharged from the anode of the fuel cell stack 11 then flows into the hydrogen gas circulation channel 46.

[0032] The gas-liquid separator 47 is installed in the hydrogen gas circulation channel 46. The gas-liquid separator 47 separates the anode-off gas that flows into the gas-liquid separator 47 via the hydrogen gas circulation channel 46 into hydrogen gas, water, and impurities.

[0033] The hydrogen circulation pump 48 is located downstream of the gas-liquid separator 47 in the flow direction of the anode-off gas in the hydrogen gas circulation channel 46. The hydrogen circulation pump 48 circulates the hydrogen gas in the hydrogen gas circuit 40 by flowing the hydrogen gas separated from the anode-off gas by the gas-liquid separator 47 into the hydrogen gas supply channel 41. The hydrogen circulation pump 48 is equipped with a motor M3. The motor M3 is electrically connected to the inverter 15. The inverter 15 converts the DC power discharged from the secondary battery 12 into AC power and supplies it to the motor M3. When the motor M3 is driven by the inverter 15, the hydrogen circulation pump 48 is driven.

[0034] <Air exhaust circuit> The air discharge circuit 50 discharges the air discharged from the fuel cell stack 11 into the atmosphere. The air discharge circuit 50 comprises an air discharge channel 51, an air pressure regulating valve 52, and a diluent 53. Cathode-off gas, which contains air and water discharged from the cathode electrode of the fuel cell stack 11, flows through the air discharge channel 51. In the air discharge channel 51, the direction in which the cathode-off gas flows is defined as the "flow direction." The upstream end of the air discharge channel 51 in the flow direction is connected to the fuel cell stack 11.

[0035] The air pressure regulating valve 52 is located downstream of the fuel cell stack 11 in the flow direction of the air discharge passage 51. The air pressure regulating valve 52 is, for example, a solenoid valve. The air pressure regulating valve 52 adjusts the air pressure in the fuel cell stack 11 by changing the valve opening.

[0036] The diluent 53 is located downstream of the air pressure regulating valve 52 in the flow direction of the air discharge channel 51. Cathode-off gas flows into the diluent 53 from the air discharge channel 51. The diluent 53 separates the supplied cathode-off gas into oxygen and water. In addition, water and impurities separated from the anode-off gas by the gas-liquid separator 47, along with hydrogen gas, are discharged from the gas-liquid separator 47 to the diluent 53. Therefore, hydrogen gas discharged from the anode electrode of the fuel cell stack 11 flows into the diluent 53. In the diluent 53, the hydrogen gas and impurities discharged from the gas-liquid separator 47 to the diluent 53 are diluted by the cathode-off gas. The hydrogen gas diluted by the diluent 53 is discharged outside the fuel cell system 10 from the downstream end of the air discharge channel 51. The water separated in the diluent 53 is stored in the water storage tank 54.

[0037] <Control device> The control device 70 comprises a processor (not shown) and a memory unit. The memory unit includes RAM (Random Access Memory) and ROM (Read Only Memory). The memory unit stores program code or instructions configured to cause the processor to execute processing. The memory unit, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The control device 70 may be composed of hardware circuits such as ASICs or FPGAs. The control device 70, which is a processing circuit, may include one or more processors that operate according to a computer program, one or more hardware circuits such as ASICs or FPGAs, or a combination thereof.

[0038] The control device 70 controls the fuel cell system 10. Based on power generation commands from a higher-level control device (not shown), it controls the flow path of the flow path control valve 33 and the valve opening of the air pressure regulating valve 52, and also controls the inverter 14 of the motor M2 to control the drive of the air compressor 32. This controls the air flow rate in the air supply flow path 31.

[0039] Furthermore, the control device 70 controls the drive of the inverter 15 of the injector 42 and motor M3 based on the power generation command. This controls the flow rate of hydrogen gas in the hydrogen gas circulation channel 46.

[0040] Furthermore, the control device 70 controls the drive of the inverter 13 of the motor M1 of the cooling water pump 24 based on the power generation command. As a result, the cooling water circulates through the cooling water circulation channel 21. The circulation of the cooling water cools the fuel cell stack 11, and the high-temperature air pumped from the air compressor 32 is cooled by the intercooler 25. As a result, the fuel cell stack 11 is supplied with temperature-controlled air at the desired temperature and flow rate, as well as hydrogen at the desired flow rate. Consequently, the fuel cell stack 11 generates the amount of power based on the power generation command.

[0041] <Secondary battery> The secondary batteries 12 are connected to the fuel cell stack 11 via a DC / DC converter (not shown). Each of the secondary batteries 12 is charged by the output power from the fuel cell stack 11, which has been transformed by the DC / DC converter.

[0042] The secondary battery 12 discharges power to the air compressor 32, the cooling water pump 24, and the hydrogen circulation pump 48. Therefore, the secondary battery 12 is the power source for the auxiliary equipment: the air compressor 32, the cooling water pump 24, and the hydrogen circulation pump 48. The secondary battery 12 comprises a plurality of cells (not shown) and a case 12a that houses these cells. The case 12a is, for example, a rectangular box.

[0043] A lithium-ion battery is used for the secondary battery 12. In lithium-ion secondary batteries 12, charging and discharging are temperature-dependent. Furthermore, the secondary battery 12 has an operating temperature range that enhances charging and discharging efficiency. If the temperature of the secondary battery 12 exceeds the operating temperature range, the degradation of the secondary battery 12 accelerates, which is undesirable.

[0044] If the temperature of the secondary battery 12 is below the operating temperature range, the internal resistance of the secondary battery 12 increases, reducing the charge and discharge efficiency, which is undesirable. In particular, if the temperature of the secondary battery 12 is below the operating temperature range, charging becomes restricted. As a result, charging of the secondary battery 12 becomes impossible, and the output power from the fuel cell stack 11 cannot charge the secondary battery 12, which is undesirable. For this reason, if the temperature of the secondary battery 12 is below the operating temperature range, it is necessary to warm up the secondary battery 12 to the operating temperature range.

[0045] <Warm-up device> The warm-up device 60 warms up the secondary battery 12 to its operating temperature range. The warm-up device 60 comprises the flow path control valve 33, the warm-up flow path 61, and the control device 70. The warm-up device 60 may also include a temperature sensor 64.

[0046] The temperature sensor 64 is installed, for example, on the outer surface of the case 12a of the secondary battery 12 in order to detect the temperature of the secondary battery 12. The temperature sensor 64 is electrically connected to the control device 70. The value detected by the temperature sensor 64 is input to the control device 70.

[0047] The flow control valve 33 comprises a first port 33a, a second port 33b, and a third port 33c. The first port 33a is connected to the outlet 25b of the intercooler 25. The second port 33b is connected to the fuel cell stack 11. Therefore, the flow control valve 33 is located in the second supply passage 31c. The third port 33c is connected to the warm-up passage 61.

[0048] The first end 61a of the warm-up passage 61 is connected to the third port 33c as described above. Therefore, the warm-up passage 61 branches off from the second supply passage 31c via the flow control valve 33. The second end 61b of the warm-up passage 61 is connected to the air discharge passage 51. The second end 61b of the warm-up passage 61 is connected downstream of the air pressure regulating valve 52 and upstream of the diluent 53 in the flow direction of the air discharge passage 51.

[0049] As shown in Figures 3 and 4, the flow control valve 33 can be switched between two positions: a first position P1 and a second position P2. The first position P1 is the position in which the first port 33a and the second port 33b are connected, and the cooling flow path 31b and the second supply path 31c are connected. The first position P1 is also the position in which the warm-up flow path 61 is blocked.

[0050] The second position P2 is the position that connects the first port 33a and the third port 33c, thereby connecting the cooling passage 31b and the warming passage 61. The second position P2 is also the position that blocks the air supply passage 31. Therefore, the flow control valve 33 allows the heat-exchanged air to flow from the second supply passage 31c to the warming passage 61.

[0051] The control device 70 switches the flow control valve 33 to either the first position P1 or the second position P2 based on the value detected by the temperature sensor 64. Therefore, the control device 70 controls the operation of the flow control valve 33.

[0052] If the temperature sensor 64 detects a value lower than a preset threshold, the control device 70 switches the flow control valve 33 to the second position P2. The threshold is set to the lower limit of the operating temperature range of the secondary battery 12. This threshold is preset through experiments or other means. If the temperature sensor 64 detects a value greater than or equal to the threshold, the control device 70 maintains the flow control valve 33 in the first position P1.

[0053] Then, when the control device 70 switches the flow control valve 33 to the first position P1, the air after heat exchange in the intercooler 25, i.e., the temperature-controlled air, is supplied to the fuel cell stack 11 via the flow control valve 33 and the second supply passage 31c. At this time, the temperature-controlled air does not flow into the warm-up passage 61. Therefore, when the flow control valve 33 is switched to the first position P1, the fuel cell stack 11 is generating electricity.

[0054] Furthermore, when the control device 70 switches the flow control valve 33 to the second position P2, the air after heat exchange in the intercooler 25, i.e., the temperature-controlled air, is supplied to the air discharge flow path 51 via the flow control valve 33 and the warm-up flow path 61. As a result, the temperature-controlled air flows into the diluent 53 via the air discharge flow path 51. Therefore, the air that has flowed through the warm-up flow path 61 is supplied to the diluent 53. Also, when the flow control valve 33 is switched to the second position P2, the temperature-controlled air does not flow into the second supply path 31c, and therefore the fuel cell stack 11 does not generate electricity.

[0055] As shown in Figure 2, a portion of the warm-up channel 61 functions as a heat sink 62. The heat sink 62 is formed by widening a portion of the warm-up channel 61. The heat sink 62 is made of a metal material with high thermal conductivity. Temperature-controlled air flows into the heat sink 62. Although not shown, heat dissipation fins (not shown) are provided inside the heat sink 62.

[0056] The heat sink 62 has a mounting surface 62a for mounting the case 12a of the secondary battery 12. The mounting surface 62a is large enough to accommodate the entire bottom surface of the case 12a. The case 12a of the secondary battery 12 is mounted on the mounting surface 62a of the heat sink 62 via a heat transfer sheet 63. Therefore, the warming channel 61 extends adjacent to the secondary battery 12 in the portion of the heat sink 62. Heat from the heat sink 62 is transferred to the secondary battery 12 via the heat transfer sheet 63 and the heat sink 62. The temperature of the air after heat exchange at the heat sink 62 is lower than that of the temperature-controlled air. The air after heat exchange at the heat sink 62 is referred to as "low-temperature air".

[0057] <Warming up of secondary batteries> Next, the warming up of the secondary battery 12 by the warming device 60 will be explained. This is before power generation by the fuel cell stack 11. At this time, the flow control valve 33 is switched to the first position P1.

[0058] The control device 70 determines whether or not to warm up the secondary battery 12 based on the value detected by the temperature sensor 64. If the temperature sensor 64 detects a value lower than a preset threshold, the control device 70 warms up the secondary battery 12. The control device 70 drives the inverter 14 to drive the air compressor 32. As a result, the inverter 14 receives discharge from the secondary battery 12, and the secondary battery 12 is warmed up by Joule heating based on its internal resistance. In other words, the secondary battery 12 is internally warmed up. Therefore, when the temperature of the secondary battery 12 falls below a preset threshold, the control device 70 uses the air compressor 32 as an auxiliary device to discharge the secondary battery 12.

[0059] Furthermore, the motor M2 is driven by the inverter 14, which drives the air compressor 32. The air compressor 32 then compresses the air. The high-temperature air discharged from the air compressor 32 is discharged into the first supply passage 31a of the air supply passage 31.

[0060] Furthermore, when warming up the secondary battery 12, the control device 70 switches the flow control valve 33 from the first position P1 to the second position P2. In other words, when warming up the secondary battery 12, the control device 70 switches the flow control valve 33 so that the air discharged from the air compressor 32, which is driven by the discharge of the secondary battery 12, and which has undergone heat exchange in the intercooler 25, flows into the warming flow path 61. As a result, the high-temperature air discharged into the first supply path 31a is cooled by heat exchange in the intercooler 25 to become temperature-controlled air, and then flows into the warming flow path 61 via the third port 33c. The temperature-controlled air that flows into the warming flow path 61 loses some heat as it flows through the warming flow path 61, and its temperature decreases.

[0061] Then, in the heat sink 62 of the warming channel 61, the secondary battery 12 is warmed by heat exchange between the secondary battery 12 and the temperature-controlled air via the case 12a and the heat transfer sheet 63. In other words, the secondary battery 12 is warmed up externally. The low-temperature air that has passed through the heat sink 62 flows into the air discharge channel 51. The low-temperature air that has flowed into the air discharge channel 51 is discharged into the atmosphere via the diluent 53.

[0062] When the temperature sensor 64 detects a value above a threshold, the control device 70 stops the warm-up of the secondary battery 12. The control device 70 switches the flow control valve 33 from the second position P2 to the first position P1. Then, the high-temperature air discharged into the first supply passage 31a is cooled by heat exchange in the intercooler 25 to become temperature-controlled air, and is then supplied to the fuel cell stack 11 via the second port 33b and the second supply passage 31c. As a result, the fuel cell stack 11 generates electricity.

[0063] According to the above embodiment, the following effects can be obtained. (1) The warming of the secondary battery 12 by the warming device 60 is performed by internal warming, which is associated with the discharge of the secondary battery 12 to the air compressor 32, and external warming, which is performed using temperature-controlled air that flows through the warming passage 61. The temperature-controlled air used for external warming is air that has undergone heat exchange in the intercooler 25 and is supplied for power generation by the fuel cell stack 11. Therefore, the temperature of the temperature-controlled air does not become excessively high. Thus, unlike external warming which uses a heater to warm up the secondary battery 12, the secondary battery 12 does not become excessively high due to heating by the external warming. Therefore, it is possible to suppress the secondary battery 12 from becoming excessively high, and thus the deterioration of the secondary battery 12 can be suppressed. As a result, the secondary battery 12 can be suitably warmed up by both internal and external warming while suppressing the deterioration of the secondary battery 12.

[0064] (2) The secondary battery 12 is warmed up using the air after heat exchange in the intercooler 25. In other words, the secondary battery 12 is warmed up using the thermal energy of the air after it has been compressed by the air compressor 32. Normally, the air compressed by the air compressor 32 is supplied to the fuel cell stack 11 after heat exchange in the intercooler 25, so the thermal energy of the air is wasted. However, the warming up of the secondary battery 12 using the warming device 60 makes effective use of the thermal energy that would otherwise be wasted, making the warming up of the secondary battery 12 using the warming device 60 extremely useful.

[0065] (3) The secondary battery 12 can be warmed up externally using the air compressor 32 necessary for power generation by the fuel cell stack 11. Therefore, the secondary battery 12 can be warmed up without using a separate heating device such as a heater. Thus, the fuel cell system 10 can warm up the secondary battery 12 effectively while keeping costs down.

[0066] (4) The warming channel 61 is equipped with a heat sink 62 for heat exchange with the secondary battery 12. The heat sink 62 enables appropriate heat exchange with the secondary battery 12. Therefore, it is possible to prevent the secondary battery 12 from being overheated or from warming up too quickly.

[0067] (5) The air that has undergone heat exchange in the intercooler 25 flows through the warming passage 61, so its temperature drops from immediately after the heat exchange in the intercooler 25. In addition, the secondary battery 12 undergoes heat exchange with the temperature-controlled air via the case 12a. Therefore, the secondary battery 12 does not undergo heat exchange with the air immediately after the heat exchange in the intercooler 25, which can more effectively suppress excessive external warming of the secondary battery 12.

[0068] This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically. ○As shown in Figure 5, the switching valve may be replaced with a flow control valve 36 instead of the flow control valve 33. The flow control valve 36 is a three-way valve. The flow control valve 36 has a first port 36a, a second port 36b, and a third port 36c. The first port 36a is connected to the outlet 25b of the intercooler 25. The second port 36b is connected to the fuel cell stack 11. The third port 36c is connected to the warm-up flow path 61.

[0069] The first end 61a of the warm-up passage 61 is connected to the third port 36c as described above. The second end 61b of the warm-up passage 61 is connected to the air discharge passage 51. The second end 61b of the warm-up passage 61 is connected downstream of the air pressure regulating valve 52 and upstream of the diluent 53 in the flow direction of the air discharge passage 51.

[0070] The flow control valve 36 can control the flow rate of temperature-controlled air flowing through both the second supply passage 31c and the warming passage 61. For example, if power generation by the fuel cell stack 11 is prioritized, the flow control valve 36 is controlled to flow a large amount of temperature-controlled air through the second supply passage 31c while a small amount of temperature-controlled air flows through the warming passage 61. Conversely, if warming up the secondary battery 12 is prioritized, the flow control valve 36 is controlled to flow a large amount of temperature-controlled air through the warming passage 61 while a small amount of temperature-controlled air flows through the second supply passage 31c. It is also possible for the flow control valve 36 to flow temperature-controlled air through only the warming passage 61 or only the second supply passage 31c.

[0071] The air supply circuit 30 is equipped with an airflow sensor 34 located downstream of the intake filter F and upstream of the air compressor 32 in the flow direction of the air supply passage 31. The airflow sensor 34 detects the airflow rate in the air supply passage 31. The airflow sensor 34 is electrically connected to the control device 70.

[0072] <Warming up of secondary batteries> This section describes the case where the secondary battery 12 is warmed up while the fuel cell stack 11 is generating power. The control device 70 determines whether or not to warm up the secondary battery 12 based on the value detected by the temperature sensor 64.

[0073] When generating power using the fuel cell stack 11 in a low-temperature environment, the control device 70 determines whether or not to warm up the secondary battery 12 based on the temperature sensor 64's detection value. If the temperature sensor 64 detects a value lower than the threshold, the control device 70 drives the inverter 14 to increase the discharge capacity of the air compressor 32. This increases the discharge rate from the secondary battery 12. As a result, the secondary battery 12 is further warmed up due to Joule heating based on its internal resistance.

[0074] The high-temperature air discharged from the air compressor 32 is discharged into the first supply passage 31a of the air supply passage 31. The control device 70 also controls the flow control valve 36 to flow a large amount of temperature-controlled air into the warm-up passage 61 while flowing a small amount of temperature-controlled air into the second supply passage 31c. At this time, the control device 70 adjusts the flow rates to the warm-up passage 61 and the second supply passage 31c, respectively, by adjusting the opening degree of the air pressure regulating valve 52 based on the detected value of the air flow sensor 34.

[0075] The high-temperature air discharged into the first supply channel 31a is then cooled by the cooling channel 31b to become temperature-controlled air, which then flows in large quantities into the warming channel 61 via the third port 36c. The secondary battery 12 is warmed by heat exchange between the secondary battery 12 and the temperature-controlled air at the heat sink 62 in the warming channel 61. In other words, the secondary battery 12 is warmed up externally.

[0076] The fuel cell system 10 may also be equipped with an auxiliary heater 65 near the secondary battery 12. The auxiliary heater 65 assists in the warming up by the warming device 60 and will not become excessively hot. In this configuration, the auxiliary heater 65 assists in the warming up of the secondary battery 12 by the warming device 60, so the warming up of the secondary battery 12 can be performed smoothly.

[0077] Furthermore, the temperature-controlled air that flows from the flow control valve 36 to the fuel cell stack 11 via the second supply channel 31c is used for power generation by the fuel cell stack 11. From the fuel cell stack 11, anode off gas flows into the hydrogen gas circulation channel 46. The gas-liquid separator 47 separates the anode off gas that has flowed into the gas-liquid separator 47 via the hydrogen gas circulation channel 46 into hydrogen gas, water, and impurities.

[0078] The cathode-off gas discharged from the fuel cell stack 11 flows into the diluent 53 via the air pressure regulating valve 52. Furthermore, the low-temperature air after warming up the secondary battery 12 joins in the air discharge channel 51 and flows into the diluent 53. In the diluent 53, the hydrogen gas and impurities discharged from the gas-liquid separator 47 to the diluent 53 are diluted by the low-temperature air and cathode-off gas.

[0079] Therefore, the temperature-controlled air that flows through the warming channel 61 becomes low-temperature air and is supplied to the diluent 53. As a result, the diluent 53 can dilute the hydrogen gas using not only cathode-off gas but also low-temperature air. Consequently, the dilution efficiency in the diluent 53 can be increased compared to when the hydrogen gas is diluted using only cathode-off gas.

[0080] ○The temperature of the secondary battery 12 does not necessarily have to be detected by a temperature sensor 64 that directly detects the temperature of the secondary battery 12. For example, a temperature sensor may be installed in the air supply channel 31, and the temperature of the secondary battery 12 may be detected indirectly from the temperature of the air in the air supply channel 31. In short, as long as the temperature of the secondary battery 12 can be detected, the method for detecting the temperature of the secondary battery 12 is not limited to directly detecting the temperature of the secondary battery 12 using a temperature sensor 64.

[0081] ○When the secondary battery 12 is warmed up by the warming device 60, the control device 70 may control the discharge from the secondary battery 12 to be directed not only to the inverter 14 of the air compressor 32 but also to the inverter 13 of the cooling water pump 24. In this case, the secondary battery 12 becomes a power source for both the air compressor 32 and the cooling water pump 24. Therefore, the cooling water pump 24 also becomes an auxiliary device. This increases the Joule heating due to the internal resistance of the secondary battery 12, thereby raising the internal warming temperature of the secondary battery 12. As a result, the warming up of the secondary battery 12 can be performed more quickly.

[0082] Alternatively, when the secondary battery 12 is warmed up by the warming device 60, the control device 70 may also discharge the secondary battery 12 not only to the inverter 14 of the air compressor 32 but also to the inverter 15 of the hydrogen circulation pump 48. In this case, the secondary battery 12 becomes a power source for both the air compressor 32 and the hydrogen circulation pump 48. Therefore, the hydrogen circulation pump 48 also becomes an auxiliary device.

[0083] ○The warm-up passage 61 may be opened to the atmosphere without being connected to the air discharge passage 51. ○The heat sink 62 is not required in the warming channel 61 of the warming device 60. In this case, the warming channel 61 may be folded multiple times to increase the area on which heat can be exchanged with the secondary battery 12.

[0084] Next, the technical concepts that can be understood from the above embodiments and alternative examples are described below. (i) The warming channel is provided with a heat sink that exchanges heat with the secondary battery. [Explanation of Symbols]

[0085] 10...Fuel cell system, 11...Fuel cell stack, 12...Secondary battery, 20...Cooling water circuit, 24...Cooling water pump as auxiliary equipment, 25...Intercooler, 31c...Second supply line, 32...Air compressor as auxiliary equipment, 33...Flow control valve as switching valve, 36...Flow control valve as switching valve, 48...Hydrogen circulation pump as auxiliary equipment, 53...Diluter, 61...Warm-up line, 65...Auxiliary heater, 70...Control device.

Claims

1. A secondary battery that powers the auxiliary equipment, Fuel cell stack and An air compressor for pressurizing and supplying air to the fuel cell stack, An intercooler that exchanges heat with a heat transfer medium before supplying the air discharged from the air compressor to the fuel cell stack, A fuel cell system comprising a supply path for supplying air after heat exchange in the intercooler to the fuel cell stack, A warming channel branching off from the supply channel and extending adjacent to the secondary battery, A switching valve that allows heat-exchanged air to flow from the supply path to the warming path, The system includes a control device for controlling the operation of the switching valve, When the temperature of the secondary battery falls below a preset threshold, the control device discharges the secondary battery using the air compressor as an auxiliary device, A fuel cell system characterized by switching the switching valve so that air discharged from the air compressor driven by the discharge and heat-exchanged in the intercooler flows into the warm-up passage.

2. The fuel cell system according to claim 1, further comprising a diluent into which hydrogen gas discharged from the anode of the fuel cell stack flows, and air flowing through the warming channel is supplied to the diluent.

3. A fuel cell system according to claim 1 or 2, comprising a cooling water circuit for supplying cooling water to the fuel cell stack and for discharging the cooling water from the fuel cell stack, wherein the cooling water circuit includes a cooling water pump for pressurizing the cooling water, and the cooling water pump is powered by the secondary battery.

4. The fuel cell system according to claim 1 or claim 2, further comprising an auxiliary heater for assisting in the warming of the secondary battery.

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