Fuel cell system

Abstract

The present invention relates to a fuel cell system in which, at low temperatures, as the power generation of the fuel cell stack (18) increases, a temperature regulator (78) adjusts the refrigerant flow to a water-cooled intercooler (52) to increase the temperature of the oxidant gas (pressurized air) supplied from the oxidant gas supplier (20) to the oxidant gas inlet (42) of the fuel cell stack (18) (see characteristic (154) in Figure 2).

Description

Technical Field

[0001] This invention relates to a fuel cell system having a fuel cell stack that generates electricity through an electrochemical reaction between fuel gas and oxidant gas.

[0002] The fuel cell system of the present invention is suitable for use in mobile vehicles such as fuel cell vehicles. Background Technology

[0003] In recent years, fuel cell vehicles (FCVs), which use hydrogen as fuel and have a lower environmental impact, have attracted attention as alternatives to gasoline cars. FCVs supply air (containing oxygen) and hydrogen as a fuel gas to the fuel cell. The electricity generated by the fuel cell drives an electric motor, thus propelling the vehicle. Therefore, unlike gasoline cars, fuel cell vehicles do not emit carbon dioxide (CO2), NOx, SOx, etc., but only water, making them environmentally friendly vehicles.

[0004] For example, Patent Document 1 discloses a fuel cell system in which, after the high-temperature oxidant gas compressed by the turbocharger is cooled in an air-cooled intercooler, it is further cooled in a water-cooled intercooler. The oxidant gas cooled by the water-cooled intercooler is then humidified by a humidifier and supplied to the fuel cell stack (Patent Document 1). Figure 1 ).

[0005] In this fuel cell system, in order to suppress the overcooling of oxidant gas caused by the air-cooled intercooler in the low-load region of the fuel cell stack during startup, a bypass flow path for bypassing the oxidant gas is arranged in parallel with the air-cooled intercooler.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: JP2014-120336A Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, in fuel cell systems without the bypass flow path arranged in parallel, in low-temperature environments, the cooled and humidified oxidant gas is supplied to the cathode flow path within the fuel cell stack, thus causing condensation within the fuel cell stack.

[0011] When condensation causes an increase in the amount of condensate (droplets), overflow occurs in the cathode flow path (Japanese: フラッディング).

[0012] Overflow can affect the electrochemical reactions (power generation reactions) of the fuel cell stack, thereby reducing the power generation efficiency of the fuel cell stack.

[0013] The purpose of this invention is to solve the above-mentioned problems.

[0014] Solution for solving the problem

[0015] One aspect of the present invention relates to a fuel cell system comprising: a fuel cell stack that generates electricity through an electrochemical reaction between fuel gas and oxidant gas; an oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; a temperature regulator that adjusts the temperature of the oxidant gas supplied by the oxidant gas supplier; an external temperature sensor that acquires the external temperature of the fuel cell stack; and a power generation sensor that acquires the power generated by the fuel cell stack. When the power generation is above a predetermined value, the temperature regulator adjusts to increase the temperature of the oxidant gas as the power generation increases.

[0016] Other aspects of the present invention relate to a fuel cell system comprising: a fuel cell stack that generates electricity through an electrochemical reaction between fuel gas and oxidant gas; an oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; a temperature regulator that adjusts the temperature of the oxidant gas supplied by the oxidant gas supplier; an external temperature sensor that acquires the external temperature of the fuel cell stack; and a power generation sensor that acquires the power generated by the fuel cell stack. When the external temperature is lower than a predetermined temperature, as the power generation increases, the temperature regulator adjusts to increase the temperature of the oxidant gas.

[0017] According to the present invention, condensation in the cathode flow path caused by the temperature difference between the internal temperature of the fuel cell stack and the temperature of the pressurized air (oxidant gas) supplied to the fuel cell stack can be suppressed, overflow in the cathode flow path can be prevented, and the reduction in power generation efficiency of the fuel cell stack can be eliminated.

[0018] The effects of the invention

[0019] The above-described objects, features, and advantages should be readily understood from the following description of embodiments with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the structure of a fuel cell vehicle equipped with the fuel cell system according to the embodiment.

[0021] Figure 2 It is a characteristic graph showing the target refrigerant flow rate and target pressurized air temperature under various power generation states relative to the power generation current density or power generation, recorded in the storage device of the control device.

[0022] Figure 3 This is a flowchart showing the sequence of refrigerant supply processes performed by the control device.

[0023] Figure 4 This is an illustration diagram that uses dashed lines to represent the flow of refrigerant at low external temperatures.

[0024] Figure 5 This is an illustration diagram that uses dashed lines to represent the flow of refrigerant at an external temperature of room temperature.

[0025] Figure 6 This is a diagram illustrating the flow of refrigerant when the air-cooled intercooler malfunctions under high load conditions in a fuel cell stack, represented by dashed lines.

[0026] Figure 7 This is a diagram illustrating the flow of refrigerant in a fuel cell stack under high load operation while the air-cooled intercooler is functioning normally. Detailed Implementation

[0027] [structure]

[0028] Figure 1 This is a schematic diagram showing the structure of a fuel cell vehicle 11 equipped with the fuel cell system 10 according to the embodiment. In addition to the fuel cell system 10, the fuel cell vehicle 11 also includes a drive unit 84, a high-voltage energy storage device 85, a load 92 including a motor for driving, and a control device 26 that controls the fuel cell vehicle 11 via control lines not shown.

[0029] In addition to the control device 26 for controlling the fuel cell system 10, the fuel cell system 10 also includes a fuel cell stack (fuel cell) 18, an oxidant gas supply device 20, a fuel gas supply device 22, and a cooling medium supply device (refrigerant supply device) 24.

[0030] Alternatively, the control device 26 may be divided into two or more control devices that control the fuel cell vehicle 11 and the fuel cell system 10 respectively.

[0031] The oxidant gas supply device 20 includes an oxidant gas supply pipe 32A to 32E, which is equipped with an oxidant gas pump (compressor) 56, an air-cooled intercooler 54, a water-cooled intercooler 52, and a humidifier 50 (humidified part). The oxidant exhaust pipe 33A to 33C includes a humidifier 50 (humidifying part) and a back pressure valve 66.

[0032] The oxidant gas supply device 20 uses an air pump 56 to compress and heat the air (external gas) drawn from the piping 32A, and then ejects the obtained oxidant gas (also called pressurized air). The high-temperature and high-compression pressurized air is cooled in an air-cooled intercooler 54 and heated or cooled in a water-cooled intercooler 52, thereby being temperature-appropriate.

[0033] The pressurized air, which has been appropriately heated, is humidified by the humidifier 50 (to make the humidity appropriate) and supplied to the oxidant gas inlet 42 of the fuel cell stack 18.

[0034] An air-cooled intercooler 54 is located at the front of the fuel cell vehicle 11. It exchanges heat between the air coming from the front of the fuel cell vehicle 11 and the oxidant gas that has been heated and compressed by the air pump 56, thereby cooling the oxidant gas. The heating (heating) and cooling processes of the water-cooled intercooler 52 will be described later.

[0035] Oxidant gas supplied from oxidant gas inlet 42 to the fuel cell stack 18 flows through the cathode flow path (not shown) within the fuel cell stack 18, is ejected from oxidant gas outlet 44 as highly humidified oxidant exhaust, and is supplied to piping 33C via humidifier 50 and back pressure valve 66.

[0036] The humidifier 50 recovers a portion of the moisture contained in the oxidant exhaust gas through its internal porous membrane, thereby humidifying the oxidant gas supplied from the water-cooled intercooler 52 and generating the aforementioned humidified oxidant gas.

[0037] The fuel gas supply device 22 includes a fuel tank (hydrogen tank) 62, a pressure reducing valve 60, and an ejector 58 in the fuel gas supply piping 34A to 34C, which serve as a fuel gas supplier.

[0038] The fuel gas supply device 22 also includes a fuel exhaust flow pipe 35A, a circulation pipe 36B, exhaust pipes 36C and 36D, and a purge valve 72. The purge valve 72 is located between the exhaust pipes 36C and 36D.

[0039] The fuel gas supply device 22 supplies fuel gas (hydrogen) that has been depressurized by the fuel tank 62 via the pressure reducing valve 60 to the fuel gas inlet 46 of the fuel cell stack 18 via the drive port and the nozzle of the ejector 58.

[0040] The fuel gas supplied from fuel gas inlet 46 to the fuel cell stack 18 flows through the anode flow path (not shown) within the fuel cell stack 18 and is ejected from fuel gas outlet 48 as fuel exhaust to pipe 35A.

[0041] With the purge valve 72 closed, the fuel exhaust injected into the pipe 35A is supplied to the inlet of the ejector 58 through the pipe 36B.

[0042] Ejector 58 uses fuel gas supplied from the drive port to draw in fuel exhaust gas supplied to the intake port to mix with it, and then ejects it from the outlet to the fuel gas inlet 46.

[0043] Furthermore, the outlet pipe 33C of the back pressure valve 66 and the outlet pipe 36D of the purge valve 72 are connected to a diluent (not shown). The diluent mixes the oxidizer exhaust with the fuel exhaust, diluting the hydrogen concentration to below a specified value.

[0044] Although not illustrated separately, the fuel cell stack 18 is, for example, formed by stacking single power-generating cells. Each single power-generating cell is held in place by separators, and has cathode and anode flow paths. The electrolyte membrane-electrode structure (MEA) is formed by holding a solid polymer membrane between cathode and anode electrodes. The separators at both ends of the stacked single power-generating cells are electrically connected to the positive terminal 38 and the negative terminal 40.

[0045] The positive terminal 38 of the fuel cell stack 18 is connected to the drive unit 84 via wiring (wire or busbar) 86, and the negative terminal 40 of the fuel cell stack 18 is connected to the drive unit 84 via wiring (wire or busbar) 88.

[0046] In each power generation cell of the fuel cell stack 18, oxidant gas supplied to the cathode electrode through the cathode flow path and hydrogen gas supplied to the anode electrode through the anode flow path are consumed by electrochemical reactions within the electrode catalyst layer to generate electricity.

[0047] The electricity generated by the generator is supplied to the drive unit 84 via positive wiring 86 and negative wiring 88. The drive unit 84 uses the supplied electricity and / or the electricity from the energy storage device 85 to drive the load (including the motor for vehicle operation) 92 via wiring 90, and to drive the air pump 56 via wiring 94.

[0048] The drive unit 84 also drives the charging and discharging of the energy storage device 85.

[0049] A current sensor 96 for measuring the generated current Ifc is inserted into wiring 86, and a voltage sensor 98 for measuring the generated voltage Vfc is disposed between wiring 86 and wiring 88. The current sensor 96 and the voltage sensor 98 constitute a power generation acquisition device 100 capable of calculating the generated power Pfc.

[0050] The refrigerant supply device 24 includes an FC cooling system (fuel cell cooling system) 74 as a refrigerant supplier and an oxidant gas temperature regulator 78.

[0051] The FC cooling system 74 includes a radiator 79, a mixing valve 77, and a refrigerant pump (WP: water pump) 76 in the piping 37A to 37J through which a cooling medium (also referred to as refrigerant) such as ethylene glycol or oil flows.

[0052] The mixing valve 77 includes an inlet valve 77A, a bypass inlet valve 77B, and an outlet valve 77C.

[0053] The temperature regulator 78 includes a water-cooled intercooler 52 and a three-way valve 80 as a flow regulator in the refrigerant flow piping 37J~37M, 37G.

[0054] The three-way valve 80 is equipped with an inlet valve 80A and outlet valves 80B and 80C.

[0055] A temperature sensor 110, which serves as an external temperature acquisition device, is installed on the piping 32A on the inlet side of the air pump 56 to measure the temperature of the external gas (air) (referred to as the external gas temperature or external temperature) Ta.

[0056] A temperature sensor 112, which serves as a pressurized air temperature acquisition device, is installed on the piping 32D on the outlet side of the water-cooled intercooler 52 to measure the temperature Tsa [°C] of the compressed oxidant gas (pressurized air).

[0057] A temperature sensor 116 for measuring the refrigerant inlet temperature (refrigerant temperature) Tinc [°C] is installed on the piping 37I near the refrigerant inlet 51 of the fuel cell stack 18.

[0058] A temperature sensor 117 for measuring the refrigerant outlet temperature (refrigerant temperature) Toutc is installed on the piping 37A near the refrigerant outlet 53 of the fuel cell stack 18.

[0059] A temperature sensor 118 is installed on the piping 35A near the fuel gas outlet 48 of the fuel cell stack 18 to measure the temperature (stack temperature) Ts of the fuel cell stack 18.

[0060] Furthermore, the refrigerant outlet temperature Toutc can be used instead of the stack temperature Ts.

[0061] A temperature sensor 120 is installed on the piping 37J near the inlet valve 80A of the three-way valve 80 to measure the temperature Tihc of the refrigerant supplied to the water-cooled intercooler 52.

[0062] Alternatively, a humidity sensor 114 may be installed on the outlet side of the humidifier 50, on the piping 32E, for measuring the humidity Ha[%) of the oxidant gas (the pressurized gas being humidified) being humidified by the humidifier 50.

[0063] In addition to the power switch 104, the control device 26 is also connected to an accelerator opening sensor (not shown), a vehicle speed sensor, and a SOC sensor of the energy storage device 85. The power switch 104 is used to start, continue (ON), or stop (OFF) the power generation operation of the fuel cell stack 18 of the fuel cell system 10.

[0064] The control device 26 is composed of an ECU (Electronic Control Unit), and one or more CPUs execute programs stored in memory, thereby performing various control functions.

[0065] The control device 26 executes a program based on information detected and acquired by various sensors and various acquisition devices (external gas temperature Ta, pressurized air temperature Tsa, stack temperature Ts≈ refrigerant temperature Toutc, refrigerant temperature Tinc) to adjust the valve opening of the pressure reducing valve 60, back pressure valve 66, purge valve 72, mixing valve 77 and three-way valve 80, which are respectively acting as adjustment valves, and controls the air pump 56, load 92 and energy storage device 85 through the drive unit 84.

[0066] [action]

[0067] Basically, the target refrigerant flow supply process (also referred to as refrigerant supply process) in the fuel cell system 10 of the fuel cell vehicle 11 configured as described above to the water-cooled intercooler 52 is described, wherein the water-cooled intercooler 52 controls (adjusts) the temperature of the oxidant gas supplied as pressurized air from the air pump 56 to the oxidant gas inlet 42 of the fuel cell stack 18 through heat exchange.

[0068] The refrigerant supply process to the water-cooled intercooler 52 is performed by the control device 26.

[0069] Figure 2 This shows the power generation current density [A / cm²] relative to the fuel cell stack 18, pre-recorded in the storage device of the control unit 26. 2 The characteristics of the target refrigerant flow rate Ftar [L / min] for various power generation states in terms of power generation [W] are 151, 152, and 153 (correspondence).

[0070] in addition, Figure 2 The relative current density (A / cm³) is also shown. 2 The characteristics of the target pressurized air temperature (target oxidizer gas temperature) Ttar [°C] for various power generation states in terms of power generation [W] are 154, 155, and 156 (correspondence).

[0071] exist Figure 2In the middle, the vertical axis shows the target refrigerant flow rate Ftar (0 L / min or more) corresponding to the target pressurized air temperature Ttar (between 45 °C and 70 °C in this embodiment).

[0072] exist Figure 2 In the middle, the horizontal axis represents the power generation current density [A / cm²]. 2 It is divided into three ranges: low power generation current density, medium power generation current density, and high power generation current density.

[0073] Power generation current density [A / cm] 2 The calculation is as follows: The control device 26 divides the power generation current Ifc[A] detected by the current sensor 96 and obtained by the control device 26 by the predetermined power generation area (area of ​​the catalyst layer) of the power generation cell.

[0074] Furthermore, it is also possible to use the power generation current density [A / cm²] on the horizontal axis. 2 The term "electric power" is replaced by "power generated [W]", which is the power generated by the control device 26 in response to the current density [A / cm²]. 2 The value is obtained by multiplying the power generation area by the power generation voltage Vfc[V] detected by voltage sensor 98 and acquired by control device 26. In this case, the power generation [W] on the horizontal axis is divided into low power generation, medium power generation, and high power generation ranges.

[0075] Here, the various power generation states of characteristics 151 to 153 used to determine the target refrigerant flow rate Ftar are explained.

[0076] The characteristic 151 represented by the dashed line shows the target refrigerant flow rate Ftar relative to the power generation current density in a power generation state under low temperature operation (external gas low temperature) conditions at a certain temperature below the freezing point of 0°C, such as around tens of degrees below zero.

[0077] The solid line represents characteristic 152, which shows the target refrigerant flow rate Ftar relative to the power generation current density in the power generation state under normal operating conditions (external gas normal temperature) at room temperature, which is 25 [°C] in this example.

[0078] The characteristic (characteristic point) 153 represented by a black dot shows the target refrigerant flow rate Ft ar in the power generation state relative to the power generation current density under high-load operating conditions of the fuel cell stack 18. Here, high-load operating conditions refer to the power generation state in which the fuel cell vehicle 11 drives on a certain long uphill road or continuously drives at high speed, and continuously drives under the high power generation current density (high power (high power) [W]) of the fuel cell stack 18 for a predetermined time, consuming a large amount of electrical power [kWh].

[0079] Furthermore, the various power generation states of characteristics 154 to 156, which are used to determine the target booster air temperature Ttar instead of the target refrigerant flow rate Ftar, are also explained.

[0080] The single-dotted line represents characteristic 154, which shows the target pressurized air temperature Ttar relative to the power generation current density in a power generation state at a temperature below the freezing point of 0°C, such as a low temperature operation (low temperature of external gas) at around tens of degrees below zero.

[0081] The characteristic 155 indicated by the double-dotted line shows the target pressurized air temperature Ttar relative to the power generation current density in the power generation state under normal operating conditions (normal external gas temperature) at room temperature, which is 25 [°C] in this example.

[0082] The characteristic (characteristic point) 156 represented by a white dot shows the target pressurized air temperature Ttar relative to the power generation current density in the power generation state under the high-load operating conditions (as described above) of the fuel cell stack 18.

[0083] Figure 3 This is a flowchart illustrating the sequence of refrigerant supply processes, which control the flow rate of refrigerant supplied from the FC cooling system (refrigerant supplier) 74 to the water-cooled intercooler 52 of the temperature regulator 78. Figure 2 The target refrigerant flow rate Ftar is shown. Figure 3 The refrigerant supply process in the flowchart is repeatedly executed by the control device 26 at a predetermined cycle.

[0084] In step S1, the control device 26 determines whether the power switch 104 is in the ON or OFF state.

[0085] When the power switch 104 is in the off state (step S1: no), the control device 26 terminates the refrigerant supply process.

[0086] With the power switch 104 in the ON state (step S1: Yes), in step S2, the control device 26 calculates the required power generation Pfcreq for the fuel cell stack 18 based on accelerator opening, vehicle speed, road gradient, etc. Also in step S2, the control device 26 controls the oxidizer gas supply device 20, including the gas pump 56, and the fuel gas supply device 22, including the fuel tank 62, to make the power generation Pfc of the fuel cell stack 18 equal to the calculated required power generation Pfcreq, and controls the FC cooling system 74, including the refrigerant pump 76, and the refrigerant supply device 24, including the water-cooled intercooler 52.

[0087] In step S3, the control device 26 acquires the external temperature (external gas temperature) Ta [°C] acquired by the temperature sensor 110, the temperature Tsa [°C] of the oxidant gas (pressurized air) acquired by the temperature sensor 112, and the refrigerant outlet temperature Toutc representing the stack temperature Ts.

[0088] In addition, in step S3, the control device 26 calculates the estimated temperature of the cathode flow path in the fuel cell stack 18 based on the refrigerant outlet temperature Toutc [°C] obtained by the temperature sensor 117.

[0089] Furthermore, in step S3, the control device 26 determines whether the external gas temperature Ta is less than a predetermined low temperature threshold Tlow (e.g., Tlow = 0 [°C]), and determines whether condensation occurs in the cathode flow path within the fuel cell stack 18 based on the refrigerant outlet temperature Toutc and the pressurized air temperature Tsa (estimated temperature of the cathode flow path within the fuel cell stack 18).

[0090] If the control device 26 determines that the external gas temperature Ta is less than the low temperature threshold Tlow and condensation occurs in the cathode flow path (step S3: Yes), the refrigerant supply process proceeds to step S4.

[0091] In step S4, the control device 26 obtains the target refrigerant flow rate Ftar by referring to the characteristics 151 of the low temperature operation (low temperature of external gas) conditions, and supplies refrigerant of the target refrigerant flow rate Ftar from the FC cooling system 74 to the water-cooled intercooler 52, thereby raising the temperature of the pressurized air and proceeding to step S1.

[0092] In step S4, as shown in feature 154, when the external temperature, i.e. the external gas temperature Ta, is less than a predetermined temperature such as the freezing point (low temperature threshold Tlow), the temperature Tsa of the pressurized air (oxidant gas) supplied to the fuel cell stack 18 is adjusted to increase as the generated power increases (the generated power increases at least from the predetermined power in the intermediate generated power).

[0093] Thus, when the external gas temperature Ta is low, the control device 26 heats the pressurized air using the water-cooled intercooler 52. This suppresses condensation caused by the temperature difference between the internal temperature of the fuel cell stack 18 and the temperature Tsa of the pressurized air (oxidant gas) supplied to the fuel cell stack 18, even at low temperatures. Consequently, the reduction in power generation efficiency of the fuel cell stack 18 can be eliminated even at low temperatures.

[0094] Because it can suppress condensation within the fuel cell stack 18, it also suppresses overflow within the cathode flow path.

[0095] Figure 4The thick dashed arrow lines indicate the flow (path) of the refrigerant in the fuel cell system 10 when the pressurized air is heated by the water-cooled intercooler 52 in step S4.

[0096] like Figure 4 As shown by the dashed arrow indicating the refrigerant path, the refrigerant, heated within the fuel cell stack 18 due to the heat of reaction and ejected from the refrigerant outlet 53, travels through piping 37A, and through piping 37C (bypass piping) to bypass the radiator 79, through the inlet valve 77B and outlet valve 77C of the mixing valve 77, and via piping 37F to the operating refrigerant pump 76. Refrigerant branching from piping 37H to piping 37J is supplied to the interior of the water-cooled intercooler 52 through the inlet valve 80A and outlet valve 80B of the three-way valve 80, and piping 37K. Inside the water-cooled intercooler 52, the refrigerant exchanges heat with the pressurized air, thus heating the pressurized air.

[0097] Furthermore, in step S4, the control device 26 adjusts the flow ratio of the outlet valve 80B and the outlet valve 80C of the three-way valve 80 to 100% and 0%, respectively.

[0098] The refrigerant cooled by the pressurized air in the water-cooled intercooler 52 flows through pipes 37M and 37G to pipe 37F. The cooled refrigerant mixes with the refrigerant heated by the heat of reaction in the fuel cell stack 18 in pipe 37F, is drawn into refrigerant pump 76, and is sprayed out of refrigerant pump 76 as heated refrigerant.

[0099] On the other hand, if it is determined that the external gas temperature Ta is above the low temperature threshold Tlow and no condensation occurs, or even if the external gas temperature Ta is below the low temperature threshold Tlow but no condensation occurs (step S3: no), the refrigerant supply process proceeds to step S5.

[0100] In step S5, the control device 26 determines whether it is in a high-load operating state. The high-load operating state refers to the state where the power generation Pfc[W] of the fuel cell stack 18 obtained by the power generation acquisition device 100 is in a high power generation region (refer to...). Figure 2 And it lasts for a predetermined period of time.

[0101] When the fuel cell vehicle 11 is in a state below medium load (referred to as normal operating state) that is not a high load operating state of the fuel cell stack 18 (e.g., driving on a long uphill road, etc.) (step S5: No), the refrigerant supply process proceeds to step S6.

[0102] In step S6, the control device 26 determines whether the temperature Tsa of the pressurized air obtained by the temperature sensor 112 exceeds the temperature Treq required for the fuel cell stack 18 to generate electricity efficiently.

[0103] If the temperature exceeds the high-efficiency power generation requirement temperature Treq (step S6: Yes), the refrigerant supply process proceeds to step S7. If the temperature does not exceed the high-efficiency power generation requirement temperature Treq (step S6: No), the refrigerant supply process proceeds to step S8.

[0104] In step S7, in order to suppress the temperature rise of the pressurized air, the control device 26 adjusts the flow ratio of the outlet valves 80B and 80C of the three-way valve 80 so that the flow rate on the outlet valve 80B side decreases by a certain amount while the flow rate on the outlet valve 80C side increases by a certain amount.

[0105] Figure 5 The dashed arrow lines indicate the flow of refrigerant after step S7. According to... Figure 5 ,and Figure 4 In contrast, the refrigerant also flows to the outlet valve 80C, which is not used for heating in the water-cooled intercooler 52. Furthermore, the temperature of the refrigerant supplied from the FC cooling system 74 to the water-cooled intercooler 52 of the temperature regulator 78 can be controlled based on the heat dissipation from the radiator 79 and the opening ratio of the input valve of the mixing valve 77.

[0106] By adjusting the refrigerant flow rate of the three-way valve 80 in step S7, the refrigerant supply flow rate to the water-cooled intercooler 52 is reduced, which can suppress the temperature rise of the pressurized air passing through the water-cooled intercooler 52.

[0107] In step S8, the control device 26 determines whether the temperature Tsa of the pressurized air obtained by the temperature sensor 112 is lower than the temperature Treq required for high-efficiency power generation of the fuel cell stack 18.

[0108] If the temperature is lower than the required high-efficiency power generation temperature Treq (step S8: Yes), the refrigerant supply process proceeds to step S9; if the temperature is equal to the required Treq temperature (step S8: Yes), the control process proceeds to step S10.

[0109] In step S9, in order to heat the pressurized air in the water-cooled intercooler 52, the control device 26 adjusts the flow ratio of the outlet valves 80B and 80C of the three-way valve 80 so that the flow rate on the outlet valve 80B side increases by a certain amount while the flow rate on the outlet valve 80C side decreases by a certain amount. In practice, the control device 26 controls the refrigerant pump 76's injection flow rate and the flow ratio of the three-way valve 80 with reference to the characteristics 152 of normal operation (external gas at room temperature), thereby achieving the target refrigerant flow rate Ftar to the water-cooled intercooler 52.

[0110] By adjusting the refrigerant flow rate through the three-way valve 80 in step S9, the refrigerant supply flow rate to the water-cooled intercooler 52 is increased, the pressurized air is heated, and the pressurized air temperature Tsa is increased.

[0111] In step S10, since (Tsa = Treq), the control device 26 maintains the target refrigerant supply flow to the water-cooled intercooler 52 to return to step S1.

[0112] The processing in steps S6 to S10 is that when the fuel cell stack 18 is under medium load, the temperature of the pressurized air supplied to the humidifier 50 by the water-cooled intercooler 52 can be adjusted by adjusting the opening of the three-way valve 80.

[0113] If the determination in step S5 above is affirmative (step S5: yes), in other words, when the fuel cell stack 18 is operating under high load, firstly, in step S11, the control device 26 determines whether the air-cooled intercooler 54 is operating normally or abnormally.

[0114] The abnormality of the air-cooled intercooler 54 determined by the control device 26 can be determined based on the following situation: even when the water-cooled intercooler 52 is controlled using the target refrigerant flow rate Ftar, the temperature Tsa of the pressurized air obtained by the temperature sensor 112 still rises abnormally.

[0115] If the control device 26 determines that the air-cooled intercooler 54 is operating normally (step S11: Yes), in step S12, as follows: Figure 6 As shown, the opening degree of the outlet valve 80B of the three-way valve 80 is set to 0% and the opening degree of the outlet valve 80C is set to 100%, thereby stopping the heating control (heat exchange) of the pressurized air performed by the water-cooled intercooler 52.

[0116] In this case, such as Figure 2 As shown in characteristic 153, the target refrigerant flow rate Ftar is set to 0.

[0117] Thus, when the fuel cell stack 18 is under high load, the flow of refrigerant from the three-way valve 80 to the water-cooled intercooler 52 is cut off. This prevents the temperature of the pressurized air, which will be cooled by the normally cooled air-cooled intercooler 54, from being raised again by the water-cooled intercooler 52. As a result, a suitable, but not excessive, temperature Tsa of the pressurized air is maintained, which satisfies the humidification performance of the humidifier 50 between the humidified oxidant exhaust gas (humidified gas) discharged from the oxidant gas outlet 44 of the fuel cell stack 18 and the pressurized air (dry air, i.e., the humidified gas).

[0118] On the other hand, if the control device 26 determines that the air-cooled intercooler 54 is not working properly (step S11: No), in step S13, if... Figure 7 As shown, the opening degree of the outlet valve 80B of the three-way valve 80 is set to 100% and the opening degree of the outlet valve 80C is set to 0%, thereby implementing temperature control (heat exchange) to cool the pressurized air using the water-cooled intercooler 52.

[0119] This temperature control prevents thermal damage to downstream components of the water-cooled intercooler 52, such as the humidifier 50 and the fuel cell stack 18, even if the air-cooled intercooler 54 malfunctions due to an abnormality.

[0120] Furthermore, in the above embodiments, a three-way valve 80 with a variable flow ratio and a mixing valve 77 are used respectively, but they can also be composed of two on-off valves respectively, and the duty cycle of each on-off valve can be adjusted to make the flow ratio variable.

[0121] [First Variation]

[0122] Alternatively, the flow rate of the outlet valves 80B and 80C of the three-way valve 80, which acts as a flow regulator, can be controlled as follows.

[0123] Alternatively, based on the difference between the target temperature (target pressurized air temperature Ttar) of the oxidant gas and the actual temperature Tsa, the flow rate of refrigerant supplied from the FC cooling system 74 (which acts as a refrigerant supplier) to the liquid-cooled heat exchanger, i.e., the water-cooled intercooler 52, via the three-way valve 80 is adjusted so that the actual temperature Tsa becomes the target pressurized air temperature Ttar. The target temperature (target pressurized air temperature Ttar) of the oxidant gas is set based on the power generation Pfc of the fuel cell stack 18 or the humidification state of the humidifier 50, and the actual temperature Tsa is obtained by the oxidant gas temperature sensor 112.

[0124] Furthermore, the humidification state of the humidifier 50 can be determined, for example, by means of the refrigerant outlet temperature Toutc and the pressurized air temperature Tsa, or by means of the humidity Ha obtained by the humidity sensor 114, based on whether it is in a state of condensation of water in the cathode flow path.

[0125] According to Modification 1, the actual temperature Tsa of the oxidant gas can be adjusted to an appropriate temperature, thereby improving the power generation efficiency of the fuel cell stack 18.

[0126] [Second variation]

[0127] Alternatively, when the external temperature Ta is below freezing, the heating process can be implemented after the temperature control of the fuel cell system 10 is completed. Figure 3Following step S2 in the flowchart, the temperature control of the fuel cell system 10 is maintained until the fuel cell vehicle 11 becomes drivable due to the electrical power Pfc generated by the fuel cell stack 18. In this way, the temperature Tsa of the oxidant gas (pressurized air) supplied to the fuel cell stack 18 can be moderated using the heat of reaction of the fuel cell stack 18, without the use of other heaters.

[0128] [Inventions that can be understood based on implementation methods and variations]

[0129] Hereinafter, the invention that can be understood based on the above embodiments and variations will be described. Furthermore, for ease of understanding, some structural elements are labeled with reference numerals used in the above embodiments, but these structural elements are not limited to the components labeled with these reference numerals.

[0130] (1) The fuel cell system 10 of the present invention comprises: a fuel cell stack 18 that generates electricity through an electrochemical reaction of fuel gas and oxidant gas; an oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; a temperature regulator 78 that adjusts the temperature of the oxidant gas supplied by the oxidant gas supplier; an external temperature sensor that acquires the external temperature of the fuel cell stack; and a power generation sensor 100 that acquires the power generation of the fuel cell stack. When the power generation is above a predetermined value, the temperature regulator adjusts to increase the temperature of the oxidant gas as the power generation increases (refer to characteristic 154).

[0131] According to the present invention, condensation in the cathode flow path caused by the temperature difference between the internal temperature of the fuel cell stack and the temperature of the pressurized air (oxidant gas) supplied to the fuel cell stack can be suppressed, overflow in the cathode flow path can be prevented, and the reduction in power generation efficiency of the fuel cell stack can be eliminated.

[0132] (2) The fuel cell system of the present invention comprises: a fuel cell stack that generates electricity through an electrochemical reaction between fuel gas and oxidant gas; an oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; a temperature regulator that adjusts the temperature of the oxidant gas supplied by the oxidant gas supplier; an external temperature sensor that acquires the external temperature of the fuel cell stack; and a power generation sensor that acquires the power generated by the fuel cell stack. When the external temperature is lower than a predetermined temperature, as the power generation increases, the temperature regulator adjusts to increase the temperature of the oxidant gas (refer to characteristic 154).

[0133] According to the present invention, condensation in the cathode flow path caused by the temperature difference between the internal temperature of the fuel cell stack and the temperature of the pressurized air (oxidant gas) supplied to the fuel cell stack can be suppressed, overflow in the cathode flow path can be prevented, and the reduction in power generation efficiency of the fuel cell stack can be eliminated.

[0134] (3) In the fuel cell system of the present invention, a refrigerant supply 74 is further provided, which supplies refrigerant for temperature adjustment to the fuel cell stack. The temperature regulator is configured to include: a liquid-cooled heat exchanger disposed in a gas piping that supplies oxidant gas ejected from the oxidant gas supply to the fuel cell stack; a piping 37K that allows the refrigerant ejected from the refrigerant supply to flow to the liquid-cooled heat exchanger; and a flow regulator that adjusts the flow rate of the refrigerant flowing in the piping.

[0135] According to the present invention, the refrigerant supply used for adjusting the temperature of the fuel cell stack can also be used for adjusting the temperature of the oxidant gas, thereby reducing the number of components in the fuel cell system and reducing costs.

[0136] (4) In the fuel cell system of the present invention, when the external temperature is below the predetermined temperature and the generated power is above the predetermined value, as the generated power increases, the flow regulator is adjusted to increase the flow rate of the refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger.

[0137] According to the present invention, when the external temperature is below a predetermined temperature and the generated power is above a predetermined value, the flow rate of refrigerant supplied from the refrigerant supply unit to the liquid-cooled heat exchanger is adjusted to increase as the generated power increases. In this case, the flow rate of the refrigerant heated by the heat of reaction generated by the electrochemical reaction of the fuel cell stack can be increased, thus effectively heating the oxidant gas using the liquid-cooled heat exchanger. This suppresses the formation of droplets within the fuel cell stack due to the temperature difference between the fuel cell stack and the oxidant gas.

[0138] (5) In the fuel cell system of the present invention, when the external temperature is higher than the predetermined temperature, as the power generation of the fuel cell stack increases, the flow regulator is adjusted to reduce the flow rate of refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger.

[0139] According to the present invention, when the external temperature is higher than a predetermined temperature and the temperature of the oxidant gas supplied to the fuel cell stack is also higher, the temperature difference between the oxidant gas and the fuel cell stack decreases, the possibility of droplet formation is reduced, and thus the supply flow rate of refrigerant to the liquid-cooled heat exchanger is reduced. As a result, oxidant gas at an appropriate temperature can be supplied to the fuel cell stack, thereby improving power generation efficiency.

[0140] (6) In the fuel cell system of the present invention, the present invention further comprises: an oxidant gas temperature sensor 112, which acquires the actual temperature of the oxidant gas supplied from the liquid-cooled heat exchanger to the fuel cell stack through the gas piping; and a humidifier 50, which is disposed on the gas piping to humidify the oxidant gas, wherein the flow regulator adjusts the flow rate of refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger based on the difference between the target temperature and the actual temperature of the oxidant gas, wherein the target temperature of the oxidant gas is set based on the power generation of the fuel cell stack or the humidification state of the humidifier, and the actual temperature is acquired by the oxidant gas temperature sensor.

[0141] According to the present invention, the flow rate of refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger is adjusted based on the difference between the target temperature of the oxidant gas and the actual temperature obtained by the oxidant gas temperature sensor. Therefore, the actual temperature of the oxidant gas can be adjusted to an appropriate temperature, thereby improving the power generation efficiency of the fuel cell stack.

[0142] Furthermore, the present invention is not limited to the embodiments described above, and various structures can be adopted without departing from the spirit of the present invention.

Claims

1. A fuel cell system (10), wherein the fuel cell system (10) comprises: A fuel cell stack (18) generates electricity through an electrochemical reaction between fuel gas and oxidant gas; An oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; Temperature regulator (78) adjusts the temperature of the oxidant gas supplied by the oxidant gas supplier; An external temperature sensor acquires the external temperature of the fuel cell stack. a power generation power obtainer (100) that obtains power generation power of the fuel cell stack; as well as A refrigerant supply unit (74) supplies refrigerant to the fuel cell stack for temperature regulation. The temperature regulator is configured to include: A liquid-cooled heat exchanger (52) is installed in the gas piping that supplies oxidant gas ejected from the oxidant gas supplier to the fuel cell stack; Piping (37J, 37G) that directs the refrigerant ejected from the refrigerant supply to the liquid-cooled heat exchanger; and A flow regulator (80) adjusts the flow rate of the refrigerant flowing in the piping. When the generated power is above a predetermined value, as the generated power increases, the temperature regulator is adjusted to increase the temperature of the oxidant gas.

2. The fuel cell system according to claim 1, characterized in that, When the external temperature is below a predetermined temperature. When the generated power is above the predetermined value, as the generated power increases, the flow regulator is adjusted to increase the flow rate of the refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger.

3. The fuel cell system according to claim 2, characterized in that, When the external temperature is higher than the predetermined temperature As the generated electricity increases, the flow regulator is adjusted to reduce the flow rate of refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger.

4. The fuel cell system according to claim 1, characterized in that, It also has: An oxidant gas temperature sensor acquires the actual temperature of the oxidant gas supplied from the liquid-cooled heat exchanger to the fuel cell stack via the gas piping; and A humidifier (50), installed in the gas piping, humidifies the oxidant gas. The flow regulator adjusts the flow rate of refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger based on the difference between the target temperature and the actual temperature of the oxidant gas. The target temperature of the oxidant gas is set based on the power generation of the fuel cell stack or the humidification status of the humidifier, and the actual temperature is obtained by the oxidant gas temperature sensor.

5. A fuel cell system, wherein the fuel cell system comprises: A fuel cell stack generates electricity through an electrochemical reaction between fuel gas and oxidant gas. An oxidant gas supplier that supplies the oxidant gas to the fuel cell stack; A temperature regulator that adjusts the temperature of the oxidant gas supplied by the oxidant gas supplier; An external temperature sensor acquires the external temperature of the fuel cell stack. a power generation power obtainer which obtains power generation power of the fuel cell stack; as well as A refrigerant supply unit that supplies refrigerant to the fuel cell stack for temperature regulation. The temperature regulator includes: A liquid-cooled heat exchanger is installed in the gas piping that supplies oxidant gas ejected from the oxidant gas supplier to the fuel cell stack; Piping that allows the refrigerant ejected from the refrigerant supply to flow to the liquid-cooled heat exchanger; and A flow regulator that adjusts the flow rate of the refrigerant flowing in the piping. When the external temperature is lower than a predetermined temperature, as the generated electricity increases, the temperature regulator adjusts to increase the temperature of the oxidant gas.

6. The fuel cell system according to claim 5, characterized in that, When the external temperature is below the predetermined temperature. When the generated power is above a predetermined value, as the generated power increases, the flow regulator is adjusted to increase the flow rate of the refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger.

7. The fuel cell system according to claim 5, characterized in that, When the external temperature is higher than the predetermined temperature. As the power generated by the fuel cell stack increases, the flow regulator is adjusted to reduce the flow rate of refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger.

8. The fuel cell system according to claim 5, characterized in that, It also has: An oxidant gas temperature sensor acquires the actual temperature of the oxidant gas supplied from the liquid-cooled heat exchanger to the fuel cell stack via the gas piping; and A humidifier, installed in the gas piping, humidifies the oxidant gas. The flow regulator adjusts the flow rate of refrigerant supplied from the refrigerant supplier to the liquid-cooled heat exchanger based on the difference between the target temperature and the actual temperature of the oxidant gas. The target temperature of the oxidant gas is set based on the power generation of the fuel cell stack or the humidification status of the humidifier, and the actual temperature is obtained by the oxidant gas temperature sensor.

Images