Fuel battery 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]

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

[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. The charge and discharge performance of the secondary battery decreases when the temperature drops, so the secondary battery is warmed up. Patent Document 1 discloses a warm-up device for a fuel cell system that uses a heater to warm up the secondary battery. In the warm-up device disclosed in Patent Document 1, the heat of the heater, which is heated by power supplied from the secondary battery, is transferred to the secondary battery to warm up the secondary battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-311218 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when warming up a secondary battery using a heater, the warm-up time by the heater can be shortened as the current flowing from the secondary battery to the heater increases, but the heater becomes excessively hot as the current flowing to the heater increases, which is undesirable as it deteriorates the secondary battery. [Means for solving the problem]

[0005] A fuel cell system for solving the above problem includes a secondary battery that serves as a power source for auxiliary equipment, a fuel cell stack, an air compressor that compresses air to the fuel cell stack, an intercooler that causes the air discharged from the air compressor to exchange heat with a heat medium before being supplied 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 includes a warm-up flow path that branches off from the supply path and extends 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 flow path, and a control device that controls the operation of the switching valve, and when the temperature of the secondary battery falls below a preset threshold value, the control device causes the air compressor to discharge from the secondary battery as the auxiliary equipment, and switches the switching valve so that the air discharged from the air compressor driven by the discharge and that has been heat exchanged in the intercooler flows into the warm-up flow path.

[0006] According to this, the secondary battery is warmed up by internal warming associated with discharge from the secondary battery to the air compressor, and external warming using air flowing through the warm-up flow path. External warming is performed using air after heat exchange in the intercooler. The air after heat exchange in the intercooler is the air supplied to the fuel cell stack, so it does not become excessively hot. Therefore, heating by external warming is not performed at an excessively high temperature, as in the case of using a heater. This makes it possible to suppress deterioration of the secondary battery due to the secondary battery becoming excessively hot. As a result, the secondary battery can be warmed up appropriately by both internal warming and external warming while suppressing deterioration of the secondary battery.

[0007] The fuel cell system may further include a diluter into which hydrogen gas discharged from the anode of the fuel cell stack flows, and air that has flowed through the warm-up flow passage may be supplied to the diluter.

[0008] According to this, the air used for external warm-up of the secondary battery can be utilized to dilute the hydrogen gas. The fuel cell system may include a cooling water circuit that supplies cooling water to the fuel cell stack and discharges the cooling water from the fuel cell stack, the cooling water circuit including a cooling water pump that pumps the cooling water, and the cooling water pump may be powered by the secondary battery.

[0009] According to this, since the secondary battery is discharged not only to the air compressor but also to the cooling water pump, the Joule heat due to the internal resistance of the secondary battery is larger than when only the air compressor is used to discharge. Therefore, the temperature of the secondary battery can be made higher than when only the air compressor is used to discharge the secondary battery, and as a result, the internal warm-up function of the secondary battery is improved, and the secondary battery can be warmed up quickly.

[0010] The fuel cell system may further include an auxiliary heater for assisting in warming up the secondary battery. According to this, the auxiliary heater can assist in warming up the secondary battery, so that the secondary battery can be warmed up more quickly. Effect of the Invention

[0011] The present invention can warm up a secondary battery while suppressing deterioration of the secondary battery. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a fuel cell system. [Diagram 2] FIG. 2 is a perspective view that illustrates a secondary battery and a warm-up flow passage. [Diagram 3] FIG. 3 is a schematic diagram showing the flow path control valve when switched to the first position. [Figure 4] FIG. 4 is a schematic diagram showing the flow path control valve when switched to the second position. [Diagram 5] FIG. 5 is a schematic diagram showing a fuel cell system according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, one embodiment of a fuel cell system will be described with reference to FIGS. <Fuel cell system> As shown in FIG. 1, the fuel cell system 10 includes a fuel cell stack 11, a coolant 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 cell units. Each of the plurality of fuel cell units is a polymer membrane type fuel cell in which a cathode electrode, an anode electrode, and an electrolyte membrane disposed between the two electrodes are stacked. The fuel cell units of the fuel cell stack 11 generate electricity through a chemical reaction between oxygen in the air and hydrogen.

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

[0016] Cooling water for cooling the fuel cell stack 11 flows through the cooling water circulation channel 21. The direction in which the cooling water flows through the cooling water circulation channel 21 is referred to as the “flow direction.” An upstream end and a downstream end of the cooling water circulation channel 21 in the flow direction are connected to the fuel cell stack 11.

[0017] The radiator 23 forms a part of the coolant circulation passage 21. The radiator 23 exchanges heat between the coolant flowing through the coolant circulation passage 21 and outside air. Thus, the coolant that has exchanged heat 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 downstream of the radiator 23 and upstream of the intercooler 25 in the flow direction of the cooling water circulation flow path 21. The cooling water pump 24 pumps the cooling water to circulate the cooling water in the cooling water circulation flow path 21. The motor M1 that drives the cooling water pump 24 is electrically connected to the inverter 13. The inverter 13 converts 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 the inverter 13, the cooling water pump 24 is driven. Therefore, the cooling water pump 24 uses the secondary battery 12 as a power source.

[0019] The intercooler 25 is provided downstream of the cooling water pump 24 and upstream of the fuel cell stack 11 in the flow direction of the cooling water circulation flow path 21. The intercooler 25 forms a part of the cooling water circulation flow path 21. The intercooler 25 exchanges heat between the cooling water flowing through the cooling water circulation flow path 21 as a heat medium and air discharged from an air compressor 32, which will be 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 passage control valve 33 serving as a switching valve.

[0021] Air to be supplied to the fuel cell stack 11 flows through the air supply flow path 31. The direction in which the air flows in the air supply flow path 31 is referred to as the "flow direction." A downstream end of the air supply flow path 31 in the flow direction is connected to the fuel cell stack 11. An upstream end of the air supply flow path 31 in the flow direction is open to the atmosphere via an intake filter F.

[0022] The air compressor 32 is provided downstream of the intake filter F in the flow direction of the air supply flow path 31. The air compressor 32 includes a motor M2. The motor M2 is electrically connected to the inverter 14. The inverter 14 converts DC power discharged from the secondary battery 12 into AC power and supplies the AC power 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 air taken in through the intake filter F and the air supply flow path 31, discharges it into the air supply flow path 31, and pressure-feeds the air to the fuel cell stack 11.

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

[0024] The air supply passage 31 includes 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 and the inlet 25a of the intercooler 25. Air that has been pressurized by the air compressor 32 and heated to a high temperature flows through the first supply passage 31a. In the following description, the air that has been pressurized by the air compressor 32 and heated to a high temperature is referred to as "high temperature air." The temperature of the high temperature air is higher than a temperature suitable for power generation in the fuel cell stack 11.

[0025] The cooling passage 31b connects the inlet 25a of the intercooler 25 and the outlet 25b of the intercooler 25. The cooling passage 31b is disposed inside the intercooler 25. Therefore, the cooling passage 31b of the air supply passage 31 is a 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 passage 31b. In the intercooler 25, heat exchange occurs between the cooling water flowing through the cooling water circulation passage 21 and the high-temperature air flowing through the cooling passage 31b. This cools the high-temperature air. Therefore, the intercooler 25 exchanges heat between the air discharged from the air compressor 32 and the cooling water before it is supplied to the fuel cell stack 11. Air whose temperature has been lowered below that of the high-temperature air by heat exchange in the intercooler 25 is referred to as "temperature-controlled air." The temperature of the temperature-controlled air is within a temperature range suitable for power generation in the fuel cell stack 11. Therefore, the intercooler 25 cools the high-temperature air to a temperature range suitable for power generation in the fuel cell stack 11 by heat exchange with the high-temperature air.

[0027] The second supply path 31c connects the outlet 25b of the intercooler 25 and the fuel cell stack 11. The temperature-controlled air that flows into the second supply path 31c is supplied to the cathode of the fuel cell stack 11. Therefore, the second supply path 31c is a supply path for supplying the air after heat exchange in the intercooler 25 to the fuel cell stack 11. In addition, a flow path control valve 33 is provided in the second supply path 31c. Therefore, the temperature-controlled air that flows into the second supply path 31c flows into the flow path 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 includes a hydrogen gas supply flow path 41, an injector 42, a hydrogen gas circulation flow path 46, a gas-liquid separator 47, and a hydrogen circulation pump 48.

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

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

[0031] The hydrogen gas circulation flow path 46 is connected to the fuel cell stack 11 and the hydrogen gas supply flow path 41 downstream of the injector 42. Anode off-gas containing hydrogen gas that did not react in the fuel cell stack 11, moisture produced by a chemical reaction between the hydrogen gas and oxygen, and impurities such as nitrogen is discharged from the anode of the fuel cell stack 11. The anode off-gas discharged from the anode of the fuel cell stack 11 flows into the hydrogen gas circulation flow path 46.

[0032] The gas-liquid separator 47 is provided in the hydrogen gas circulation flow path 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 flow path 46 into hydrogen gas, water, and impurities.

[0033] The hydrogen circulation pump 48 is provided downstream of the gas-liquid separator 47 in the flow direction of the anode off-gas in the hydrogen gas circulation flow path 46. The hydrogen circulation pump 48 circulates hydrogen gas in the hydrogen gas circuit 40 by causing the hydrogen gas separated from the anode off-gas by the gas-liquid separator 47 to flow into the hydrogen gas supply flow path 41. The hydrogen circulation pump 48 includes a motor M3. The motor M3 is electrically connected to the inverter 15. The inverter 15 converts 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 air discharged from the fuel cell stack 11 to the atmosphere. The air discharge circuit 50 includes an air discharge flow path 51, an air pressure regulating valve 52, and a diluter 53. Cathode off-gas containing air and water discharged from the cathode of the fuel cell stack 11 flows through the air discharge flow path 51. In the air discharge flow path 51, the direction in which the cathode off-gas flows is defined as the "flow direction." An upstream end of the air discharge flow path 51 in the flow direction is connected to the fuel cell stack 11.

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

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

[0037] <Control device> The control device 70 includes a processor (not shown) and a storage unit. The storage unit includes a RAM (Random Access Memory) and a ROM (Read Only Memory). The storage unit stores program code or instructions configured to cause the processor to execute a process. The storage unit, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The control device 70 may be configured by a hardware circuit such as an ASIC or an FPGA. 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 an ASIC or an FPGA, or a combination thereof.

[0038] The control device 70 controls the fuel cell system 10. Based on a power generation command from a higher-level control device (not shown), the control device 70 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 flow rate of air in the air supply flow path 31.

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

[0040] Furthermore, the control device 70 controls the driving of the inverter 13 of the motor M1 of the cooling water pump 24 based on the power generation command. This causes the cooling water to circulate through the cooling water circulation flow path 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 in the intercooler 25. As a result, temperature-controlled air of the desired temperature and flow rate is supplied to the fuel cell stack 11, and hydrogen is supplied at the desired flow rate. As a result, 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 secondary battery 12 is charged by the output power from the fuel cell stack 11 that has been transformed by the DC / DC converter.

[0042] The secondary battery 12 discharges 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 devices, that is, the air compressor 32, the cooling water pump 24, and the hydrogen circulation pump 48. The secondary battery 12 includes a plurality of cells (not shown), and a case 12a that houses the plurality of cells. The case 12a is, for example, in the shape of a rectangular box.

[0043] A lithium ion battery is used as the secondary battery 12. In the lithium ion secondary battery 12, charging and discharging are temperature dependent. Also, the secondary battery 12 has an operating temperature range for increasing the charging and discharging efficiency. If the temperature of the secondary battery 12 is higher than the operating temperature range, the deterioration of the secondary battery 12 will be accelerated, which is undesirable.

[0044] If the temperature of the secondary battery 12 is lower than the operating temperature range, the internal resistance of the secondary battery 12 increases, and the charge / discharge efficiency decreases, which is undesirable. In particular, if the temperature of the secondary battery 12 is lower than the operating temperature range, restrictions are imposed on charging. This makes it impossible to charge the secondary battery 12, and therefore it is undesirable that the output power from the fuel cell stack 11 cannot be used to charge the secondary battery 12. For this reason, if the temperature of the secondary battery 12 is lower than the operating temperature range, it is necessary to warm up the secondary battery 12 to the operating temperature range.

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

[0046] The temperature sensor 64 is disposed, 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 detection value of the temperature sensor 64 is input to the control device 70.

[0047] The flow path control valve 33 includes 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. Thus, the flow path control valve 33 is provided in the second supply path 31c. The third port 33c is connected to the warm-up flow path 61.

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

[0049] 3 and 4, the flow passage control valve 33 can be switched between two positions, a first position P1 and a second position P2. The first position P1 is a position where the first port 33a communicates with the second port 33b, and the cooling flow passage 31b communicates with the second supply passage 31c. The first position P1 is also a position where the warm-up flow passage 61 is blocked.

[0050] The second position P2 is a position where the first port 33a communicates with the third port 33c, and where the cooling passage 31b communicates with the warm-up passage 61. The second position P2 is also a position where the air supply passage 31 is blocked. Therefore, the passage control valve 33 allows the air after heat exchange to flow from the second supply passage 31c to the warm-up passage 61.

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

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

[0053] When the flow path control valve 33 is switched to the first position P1 by the control device 70, 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 path control valve 33 and the second supply path 31c. At this time, the temperature-controlled air does not flow into the warm-up flow path 61. Therefore, when the flow path control valve 33 is switched to the first position P1, the fuel cell stack 11 is generating power.

[0054] Furthermore, when the flow path control valve 33 is switched to the second position P2 by the control device 70, 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 path control valve 33 and the warm-up flow path 61. As a result, the temperature-controlled air flows into the diluter 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 diluter 53. Furthermore, when the flow path 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 power.

[0055] 2, a portion of the warm-up passage 61 functions as a heat sink 62. The heat sink 62 is formed by widening a portion of the warm-up passage 61. The heat sink 62 is formed 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 on which the case 12a of the secondary battery 12 is placed. The mounting surface 62a is large enough to accommodate the entire lower surface of the case 12a. The case 12a of the secondary battery 12 is placed on the mounting surface 62a of the heat sink 62 via a heat transfer sheet 63. Therefore, the warm-up flow path 61 extends adjacent to the secondary battery 12 at 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-controlled air that has flowed into the warm-up flow path 61 exchanges heat with the secondary battery 12. The temperature of the air after heat exchange in the heat sink 62 is lower than that of the temperature-controlled air. The air after heat exchange in the heat sink 62 is referred to as "low-temperature air."

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

[0058] The control device 70 determines, based on the detection value of the temperature sensor 64, whether or not to warm up the secondary battery 12. When the detection value of the temperature sensor 64 is lower than a preset threshold value, the control device 70 warms up the secondary battery 12. The control device 70 drives the inverter 14 to drive the air compressor 32. Then, the inverter 14 discharges the secondary battery 12, and the secondary battery 12 warms up by generating Joule heat based on 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 value, the control device 70 causes the air compressor 32 as an auxiliary device to discharge the secondary battery 12.

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

[0060] Furthermore, when warming up the secondary battery 12, the control device 70 switches the flow path control valve 33 from the first position P1 to the second position P2. That is, when warming up the secondary battery 12, the control device 70 switches the flow path control valve 33 so that the air discharged from the air compressor 32 driven by the discharge of the secondary battery 12 and heat exchanged in the intercooler 25 flows into the warm-up flow path 61. Then, 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 warm-up flow path 61 via the third port 33c. The temperature-controlled air that has flowed into the warm-up flow path 61 releases some heat while flowing through the warm-up flow path 61, decreasing its temperature.

[0061] Then, in the heat sink 62 of the warm-up flow path 61, the secondary battery 12 is warmed up 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 flow path 51. The low-temperature air that has flowed into the air discharge flow path 51 passes through the diluter 53 and is discharged to the atmosphere.

[0062] When the detection value of the temperature sensor 64 becomes equal to or greater than the threshold value, the control device 70 stops warming up the secondary battery 12. The control device 70 switches the flow path control valve 33 from the second position P2 to the first position P1. Then, the high-temperature air discharged into the first supply path 31a is cooled by heat exchange in the intercooler 25 to become temperature-regulated air, and is then supplied to the fuel cell stack 11 via the second port 33b and the second supply path 31c. This causes the fuel cell stack 11 to generate electricity.

[0063] According to the above embodiment, the following effects can be obtained. (1) The warm-up of the secondary battery 12 by the warm-up device 60 is performed by internal warm-up accompanying discharge of the secondary battery 12 to the air compressor 32 and external warm-up using the temperature-controlled air flowing through the warm-up flow path 61. The temperature-controlled air used for external warm-up is air after heat exchange in the intercooler 25, and is the air supplied for power generation of the fuel cell stack 11. Therefore, the temperature of the temperature-controlled air does not become excessively high. Therefore, unlike external warm-up using a heater to warm up the secondary battery 12, the secondary battery 12 does not become excessively high temperature due to heating by the external warm-up. Therefore, the secondary battery 12 can be prevented from becoming excessively high temperature, and deterioration of the secondary battery 12 can be suppressed. As a result, the secondary battery 12 can be appropriately warmed up by both internal warm-up and external warm-up while suppressing deterioration of the secondary battery 12.

[0064] (2) The secondary battery 12 is warmed up using air that has been heat exchanged in the intercooler 25. In other words, the secondary battery 12 is warmed up by utilizing the thermal energy of the air that 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, and the thermal energy of the air is simply wasted. However, the warming up of the secondary battery 12 by the warming up device 60 effectively utilizes the thermal energy that would have been wasted, and therefore the warming up of the secondary battery 12 by the warming up device 60 is extremely useful.

[0065] (3) The external warm-up of the secondary battery 12 can be performed using the air compressor 32 required for power generation in the fuel cell stack 11. Therefore, the secondary battery 12 can be warmed up without using a separate heating device such as a heater. Therefore, the fuel cell system 10 can appropriately warm up the secondary battery 12 while suppressing increases in costs.

[0066] (4) The warm-up flow path 61 includes 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. This prevents the secondary battery 12 from being heated to an excessively high temperature or from being warmed up too quickly.

[0067] (5) The air that has undergone heat exchange in the intercooler 25 flows through the warm-up flow path 61, and therefore its temperature drops compared to immediately after heat exchange in the intercooler 25. In addition, the secondary battery 12 exchanges heat with the temperature-controlled air via the case 12a. Therefore, the secondary battery 12 does not exchange heat with the air that has undergone heat exchange in the intercooler 25, and excessive external warm-up of the secondary battery 12 can be more suitably prevented.

[0068] This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction. As shown in Fig. 5, the switching valve may be a flow control valve 36 instead of the flow path 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 diluter 53 in the flow direction of the air discharge passage 51.

[0070] The flow control valve 36 can control the flow rate of the temperature regulated air flowing through both the second supply path 31c and the warm-up path 61. For example, when priority is given to power generation by the fuel cell stack 11, the flow control valve 36 is controlled to flow a large amount of temperature regulated air through the second supply path 31c while flowing a small amount of temperature regulated air through the warm-up path 61. Conversely, when priority is given to warm-up of the secondary battery 12, the flow control valve 36 is controlled to flow a large amount of temperature regulated air through the warm-up path 61 while flowing a small amount of temperature regulated air through the second supply path 31c. The flow control valve 36 can also flow the temperature regulated air only through the warm-up path 61 or the second supply path 31c.

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

[0072] <Warming up the secondary battery> A description will be given of a case where the secondary battery 12 is warmed up during power generation by the fuel cell stack 11. The control device 70 determines, based on a value detected by the temperature sensor 64, whether or not to warm up the secondary battery 12.

[0073] When the fuel cell stack 11 is generating power in a low-temperature environment, the control device 70 determines, based on the value detected by the temperature sensor 64, whether or not to warm up the secondary battery 12. When the detection value of the temperature sensor 64 is lower than the threshold value, the control device 70 drives the inverter 14 to increase the discharge capacity of the air compressor 32. This increases the amount of discharge from the secondary battery 12. This causes the secondary battery 12 to generate more Joule heat due to internal resistance, warming up the inside.

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

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

[0076] The fuel cell system 10 may include an auxiliary heater 65 near the secondary battery 12. The auxiliary heater 65 assists the warm-up by the warm-up device 60, and therefore does not become excessively hot. In this configuration, the auxiliary heater 65 can assist the warm-up of the secondary battery 12 by the warm-up device 60, so that the secondary battery 12 can be warmed up smoothly.

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

[0078] The cathode off-gas discharged from the fuel cell stack 11 flows into the diluter 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 flow path 51 and flows into the diluter 53. Then, in the diluter 53, the hydrogen gas and impurities discharged from the gas-liquid separator 47 to the diluter 53 are diluted by the low-temperature air and the cathode off-gas.

[0079] Therefore, the temperature-controlled air that has flowed through the warm-up flow passage 61 becomes low-temperature air and is supplied to the diluter 53. This allows the diluter 53 to dilute the hydrogen gas using not only the cathode off-gas but also the low-temperature air. Therefore, the dilution efficiency in the diluter 53 can be improved compared to the case where the hydrogen gas is diluted only by the cathode off-gas.

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

[0081] When the warm-up device 60 warms up the secondary battery 12, the control device 70 may control the secondary battery 12 to discharge 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 serves as a power source for the cooling water pump 24 in addition to the air compressor 32. Therefore, the cooling water pump 24 also serves as an auxiliary device. This increases Joule heat based on the internal resistance of the secondary battery 12, so that the internal warm-up temperature of the secondary battery 12 can be increased. As a result, the secondary battery 12 can be warmed up more quickly.

[0082] Alternatively, when the warm-up device 60 warms up the secondary battery 12, the control device 70 may cause the secondary battery 12 to discharge 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 serves as a power source for the hydrogen circulation pump 48 in addition to the air compressor 32. Therefore, the hydrogen circulation pump 48 also serves as an auxiliary machine.

[0083] The warm-up passage 61 may be open to the atmosphere without being connected to the air exhaust passage 51 . The warm-up passage 61 of the warm-up device 60 does not necessarily have to include the heat sink 62. In this case, the warm-up passage 61 may be bent back multiple times to increase the area available for heat exchange with the secondary battery 12.

[0084] Next, the technical ideas that can be understood from the above-described embodiment and other examples will be described below. (i) The warm-up flow passage is provided with a heat sink for exchanging 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 path, 32... air compressor as auxiliary equipment, 33... flow path control valve as switching valve, 36... flow rate control valve as switching valve, 48... hydrogen circulation pump as auxiliary equipment, 53... diluter, 61... warm-up flow path, 65... auxiliary heater, 70... control device.

Claims

1. A secondary battery that serves as a power source for auxiliary equipment; A fuel cell stack; an air compressor for compressing air to the fuel cell stack; an intercooler for exchanging heat between the air discharged from the air compressor and a heat medium before the air is supplied to the fuel cell stack; a supply passage for supplying the air after heat exchange in the intercooler to the fuel cell stack, a warm-up flow path branching from the supply path and extending adjacent to the secondary battery; a switching valve that allows air after heat exchange to flow from the supply passage to the warm-up passage; A control device for controlling the operation of the switching valve, When a temperature of the secondary battery becomes lower than a preset threshold value, the control device causes the air compressor to discharge from the secondary battery as the auxiliary device, and the switching valve is switched 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. 2. The fuel cell system according to claim 1, further comprising a diluter into which hydrogen gas discharged from an anode of the fuel cell stack flows, and the air that has flowed through the warm-up passage is supplied to the diluter.

3. 3. The fuel cell system according to claim 1, further comprising a cooling water circuit that supplies cooling water to the fuel cell stack and discharges the cooling water from the fuel cell stack, the cooling water circuit including a cooling water pump that pumps the cooling water, the cooling water pump being powered by the secondary battery.

4. 3. The fuel cell system according to claim 1, further comprising an auxiliary heater that assists in warming up the secondary battery.

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