fuel cell system

Abstract

To provide a fuel cell system that can appropriately consume the regenerative power and prevent the freezing of a fuel cell even when the regenerative power is generated while a fuel cell vehicle is descending a long downhill.SOLUTION: A fuel cell system 10 supplies, from a fuel cell stack 18 or a power storage device 44, electric power for causing a motor 46 to generate a driving force. In a case where the power storage device 44 cannot be charged with regenerative power generated by the motor 46, the regenerative power is first consumed by a heater 82 alone. Then, while the regenerative power is consumed by the heater 82, the waste heat of the heater 82 is recovered by the fuel cell stack 18 to warm the fuel cell stack 18. When the temperature of the fuel cell stack 18 rises to a first threshold temperature Th1, the regenerative power is consumed by an air pump 28 alone.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system that drives a motor using electric power generated by a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas. [Background technology]

[0002] In recent years, research and development into fuel cells (FCs) has been conducted to contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable, and advanced energy.

[0003] For example, Japanese Patent Application Laid-Open No. 2019-140854 discloses a technology (referred to as the first technology) in which, when the regenerative power of the motor of a fuel cell vehicle becomes surplus, the surplus regenerative power is consumed by a heating section (heater) of an air conditioning circuit (see

[0024] of the above publication).

[0004] Furthermore, the fuel cell vehicle disclosed in the publication also discloses a technology (referred to as the second technology) that circulates the heat medium between the air conditioning circuit and the fuel cell when the temperature of the heat medium flowing through the heating section reaches an upper limit temperature while the regenerative power is being consumed (

[0025] of the publication).

[0005] Furthermore, as another example of the fuel cell vehicle disclosed in the publication, even if the temperature of the heat medium flowing through the heating section reaches an upper limit temperature while the regenerative power is being consumed, if the temperature of the fuel cell has not reached the upper limit temperature, a technology (referred to as the third technology) is disclosed in which the heat medium is circulated between the air conditioning circuit and the fuel cell (

[0029] of the publication). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-140854 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the fuel cell vehicle disclosed in the publication does not take into account the temperature of the fuel cell during control using the first and second techniques, which means that the temperature of the fuel cell cannot be accurately controlled.

[0008] Therefore, when a fuel cell vehicle is generating regenerative power while traveling down a long slope, there is a problem that the fuel cell system may freeze.

[0009] Furthermore, in the fuel cell system disclosed in the publication, when the third technique cannot be applied, the process is terminated, and therefore there is a problem in that the regenerative power cannot be consumed. The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0010] a fuel cell temperature sensor for detecting the temperature of the heat medium that controls the temperature of the fuel cell; a heater heat medium supply device for branching the heat medium and supplying it to a heater; a heater heat medium temperature sensor for detecting the temperature of the heat medium that controls the temperature of the heater; and a switching valve for connecting or blocking the heat medium flowing through the fuel cell heat medium supply device and the heat medium flowing through the heater heat medium supply device; and In the fuel cell system, which supplies auxiliary electric power to the fuel cell heat medium supply device and the heater heat medium supply device and supplies driving electric power to generate driving force to a motor, when the regenerative electric power generated in the motor cannot be charged to the power storage device, if the fuel cell heat medium temperature is less than a first threshold temperature and the temperature difference obtained by subtracting the fuel cell heat medium temperature from the heater heat medium temperature is equal to or greater than a threshold temperature difference, the switching valve is switched to a communicating state to increase the fuel cell heat medium temperature, and if the fuel cell heat medium temperature is equal to or greater than the first threshold temperature, the switching valve is switched to a blocking state to increase the rotation speed of the air pump so that the regenerative electric power is consumed by the air pump, performing power consumption control. [Effects of the Invention]

[0011] According to the present disclosure, when regenerative power is generated in the motor and cannot be charged to the power storage device, the regenerative power is consumed in the following order: heater alone, heater-fuel cell combination, and air pump alone. This allows the regenerative power to be consumed appropriately without freezing the fuel cell system.

[0012] When regenerative power is being generated, power generation by the fuel cell is idled, and the stack temperature is low. If the air pump is rotated at high speed (normally) using regenerative power when the stack temperature is low, the fuel cell system may freeze. In contrast, this invention provides a period in which the heater consumes regenerative power alone, and a period in which the heater and fuel cell consume regenerative power in combination, before the air pump consumes regenerative power alone. This allows for accurate control of the fuel cell temperature and ensures reliable consumption of regenerative power, ultimately contributing to improved energy efficiency. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a fuel cell vehicle incorporating a fuel cell system according to an embodiment. [Figure 2] FIG. 2 is a block diagram of the regenerative power consumption system including a detailed configuration of the regenerative power consumption control unit in the control device shown in FIG. [Figure 3] FIG. 3 is a flowchart illustrating the operation of the fuel cell system. [Figure 4] FIG. 4 is a diagram illustrating the current-voltage characteristics of the fuel cell stack. [Figure 5] Fig. 5A is an explanatory diagram showing the flow of the heat medium when the switching valve is in a blocked state, and Fig. 5B is an explanatory diagram showing the flow of the heat medium when the switching valve is in a communicating state. [Figure 6] FIG. 6 is a table illustrating the power consumption control of regenerative power. [Figure 7] FIG. 7 is a timing chart illustrating an example of power consumption of regenerated power. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Embodiment] [composition] FIG. 1 is a schematic diagram of a fuel cell vehicle 12 incorporating a fuel cell system 10 according to an embodiment of the present invention.

[0015] The fuel cell system 10 can be incorporated into other moving objects other than the fuel cell vehicle 12, such as ships, flying objects such as aircraft, robots, and the like.

[0016] The fuel cell vehicle 12 is composed of a fuel cell system 10, an output unit 16 electrically connected to the fuel cell system 10, and a control device 15 that controls the entire fuel cell vehicle 12 (including the fuel cell system 10 and the output unit 16).

[0017] The control device 15 may not be one, but may be divided into two or more control devices, for example, one for the fuel cell system 10 and one for the output unit 16.

[0018] The fuel cell system 10 is composed of a fuel cell stack (FC stack, or simply referred to as a fuel cell (FC)) 18, a fuel tank (hydrogen tank, fuel gas tank) 20, an oxidant gas supply device 22, a fuel gas supply device 24, a fuel cell heat medium supply device 26, and a heater heat medium supply device 27. The oxidant gas supply device 22 includes an air pump (AP) 28 and a humidifier (HUM) 30 .

[0019] The fuel gas supply device 24 includes an injector (INJ) 32, an ejector 34, and a gas-liquid separator 36. The injector 32 may be replaced with a pressure reducing valve.

[0020] The fuel cell heat medium supply device 26 includes a heat medium pump (WP) 38 , a thermo valve 37 , and a radiator 39 .

[0021] The heater heat medium supply device 27 includes a heat medium pump 81, a heater 82, a heater core 84, a switching valve 85 which is a three-way valve, heat medium flow paths 143, 144, 146, 148 which communicate with these, and a temperature sensor 83. The heater heat medium supply device 27 is configured as a part of an air conditioner. The output unit 16 includes a voltage conversion unit 42, a power storage unit 43, and a motor (electric motor) 46.

[0022] The voltage conversion unit 42 includes an inverter 45, a DC / DC converter 40 which is a step-up converter (SUC), and a DC / DC converter 41 which is a step-up / step-down converter (SUDC).

[0023] The power storage unit 43 includes a high voltage Vbh [V] power storage device (high voltage battery, HV BAT) 44, a DC / DC converter 47 which is a step-down converter (SDC), and a low voltage Vbl [V] power storage device (low voltage battery, LV BAT) 48.

[0024] The loads of the power storage unit 43, which is equipped with a voltage conversion unit 42 and a high-voltage Vbh power storage device 44 connected to the fuel cell stack 18, include a motor 46 as a main engine, an air pump 28 as a high-voltage auxiliary device supplied with power from the high-voltage Vbh power storage device 44, and low-voltage auxiliary devices (for example, the air conditioner, various sensors, various solenoid valves, the injector 32, and the heat medium pump 38, each of which will be described later). The low-voltage auxiliary devices are supplied with power from the power storage device 48, which generates the low voltage Vbl.

[0025] The heater 82 is configured to be able to receive the high voltage Vinv related to the regenerative power from the voltage conversion unit 42. Although not shown, the heater 82 is also configured to be able to consume power (generate heat) by receiving the high voltage Vbh during heating. Instead of the high voltage Vinv, the heater 82 may be supplied with the high voltage Vbh obtained by lowering the regenerative power by the DC / DC converter 41.

[0026] The DC / DC converter 40 converts the output voltage Vfc, which is the DC voltage generated by the fuel cell stack 18 , into a step-up voltage, and applies a high driving voltage to the DC end of the inverter 45 and the DC / DC converter 41 .

[0027] The DC / DC converter 41 steps down the high voltage for driving to a high voltage Vbh, which is the battery voltage of the power storage device 44, and charges the power storage device 44 with the high voltage Vbh.

[0028] The DC / DC converter 47 steps down the high voltage Vbh to a low voltage Vbl, and charges the power storage device 48 with the low voltage Vbl.

[0029] The high voltage Vinv obtained by stepping up the high voltage Vbh by the DC / DC converter 41 and / or the high voltage Vinv obtained by stepping up the output voltage Vfc by the DC / DC converter 40 are applied to the DC end of the inverter 45 as drive voltages.

[0030] The inverter 45 converts the high voltage Vinv, which is a direct current, into a three-phase alternating current to drive the motor 46 . The fuel cell vehicle 12 runs on the driving force generated by the motor 46 .

[0031] The inverter 45 converts the regenerative voltage of the motor 46 into a high DC voltage Vinv. This high DC voltage Vinv is stepped down to a high voltage Vbh by the DC / DC converter 41. The high voltage Vbh is applied to the power storage device 44 to charge the power storage device 44.

[0032] When the SOC (state of charge) of the power storage device 44 exceeds the full charge threshold SOCth for the fully charged state, the regenerative voltage (regenerative power) of the high voltage Vinv is consumed (i.e., wasted) by the heater 82 or the air pump 28. The SOC of the power storage device 44 is detected by the SOC sensor 49 and acquired by the control device 15.

[0033] The fuel cell stack 18 is made up of a plurality of stacked power generating cells 50. Each power generating cell 50 includes a membrane electrode assembly 52 and separators 53 and 54 that sandwich the membrane electrode assembly 52.

[0034] The membrane electrode assembly 52 includes a solid polymer electrolyte membrane 55, which is, for example, a thin film of perfluorosulfonic acid containing water, and a cathode electrode 56 and an anode electrode 57 that sandwich the solid polymer electrolyte membrane 55.

[0035] The cathode electrode 56 and the anode electrode 57 each have a gas diffusion layer (not shown) made of carbon paper or the like. The surface of the gas diffusion layer is uniformly coated with porous carbon particles carrying a platinum alloy on its surface, thereby forming an electrode catalyst layer (not shown). The electrode catalyst layer is formed on both sides of the solid polymer electrolyte membrane 55.

[0036] On the surface of one separator 53 facing the electrolyte membrane electrode assembly 52, a cathode flow path (oxidant gas flow path) 58 is formed that connects the oxidant gas inlet communication port 101 and the oxidant gas outlet communication port 102 and runs along the cathode electrode 56.

[0037] On the surface of the other separator 54 facing the membrane electrode assembly 52, an anode flow path (fuel gas flow path) 59 is formed that connects the fuel gas inlet communication port 103 and the fuel gas outlet communication port 104 and runs along the anode electrode 57.

[0038] A voltage sensor 110 that detects the output voltage Vfc of the fuel cell stack 18 is provided between the wiring that connects the positive terminal 108 and the negative terminal 106 to the DC / DC converter 40. Furthermore, a current sensor 112 that detects the generated current Ifc is provided in the wiring that connects the positive terminal 108 to the DC / DC converter 40.

[0039] The voltage sensor 110 and the current sensor 112 form a power generation state acquisition unit 115 that detects the generated power as the power generation state. The voltage sensor 110 may be provided for each power generation cell 50 or for each set of multiple power generation cells 50.

[0040] The air pump 28 is composed of an air pump inverter (not shown) to which the high voltage Vbh of the high-voltage storage device 44 is applied, and a mechanical supercharger driven by an air pump motor (not shown) controlled by the three-phase AC output of the air pump inverter.

[0041] The air pump 28 has functions such as drawing in outside air (atmospheric air) from the outside air intake 113, pressurizing it, and supplying it to the fuel cell stack 18 through the humidifier 30.

[0042] The humidifier 30 has a flow path 31A and a flow path 31B. Air (oxidant gas) that has been compressed, heated, and dried by the air pump 28 flows through the flow path 31A. Oxidant off-gas, which is exhaust gas discharged from the oxidant gas outlet communication port 102 of the fuel cell stack 18 via the oxidant off-gas outlet 92, flows through the flow path 31B.

[0043] The humidifier 30 has a function of humidifying the oxidant gas supplied from the air pump 28. That is, the humidifier 30 humidifies the oxidant gas by transferring moisture contained in the oxidant off-gas from the flow path 31B to the supply gas (oxidant gas) flowing through the internal porous membrane to the flow path 31A, and supplies the humidified oxidant gas to the fuel cell stack 18 through the oxidant gas inlet 91.

[0044] The oxidizing gas supply flow path 62 (including the oxidizing gas supply flow paths 62A and 62B) from the outside air intake 113 to the oxidizing gas inlet 91 is provided with an air flow sensor (AFS: flow rate sensor) 116, an air pump 28, an inlet-side sealing valve 118, and a humidifier 30, in this order from the outside air intake 113. Note that flow paths such as the oxidizing gas supply flow path 62 drawn with double lines are formed by piping (the same applies hereinafter).

[0045] The opening degree of the inlet-side sealing valve 118 can be variably controlled by the control device 15, and opens and closes the oxidizing gas supply channel 62.

[0046] The oxidant off-gas discharge flow path 63 communicating with the oxidant off-gas outlet 92 is provided with a humidifier 30 and an outlet-side seal valve 120 which also functions as a back pressure valve, in this order from the oxidant off-gas outlet 92. The valve opening degree of the outlet-side seal valve 120 can be variably controlled by the control device 15, and the outlet-side seal valve 120 opens and closes the oxidant off-gas discharge flow path 63.

[0047] A bypass flow path 66 that connects the oxidant gas supply flow path 62 and the oxidant off-gas discharge flow path 63 is provided between the suction port of the inlet-side sealing valve 118 and the discharge port of the outlet-side sealing valve 120. A bypass valve 122 that opens and closes the bypass flow path 66 is provided in the bypass flow path 66.

[0048] The opening degree of the bypass valve 122 can be variably controlled by the control device 15. The bypass valve 122 adjusts the flow rate of the oxidant gas that bypasses the fuel cell stack . The junction of the bypass flow path 66 and the oxidant off-gas discharge flow path 63 communicates with the discharge flow path 64 .

[0049] The fuel tank 20 is a container that includes an electromagnetically operated hydrogen shutoff valve 21 and stores highly purified hydrogen compressed at high pressure.

[0050] The fuel gas (hydrogen) discharged from the fuel tank 20 passes through the injector 32 and ejector 34 provided in the fuel gas supply flow path 72, and is supplied to the inlet of the anode flow path 59 via the fuel gas inlet 93 and fuel gas inlet communication port 103 of the fuel cell stack 18.

[0051] In this case, the fuel gas supply passage 72 is provided with a pressure sensor 73 that detects (measures) the gas pressure (anode pressure) Pa of the fuel gas in the fuel gas supply passage 72 .

[0052] The outlet of the anode flow path 59 is connected to the inlet 151 of the gas-liquid separator 36 via the fuel gas outlet communication port 104, the fuel off-gas outlet 94, and the fuel off-gas discharge flow path 74 for the fuel off-gas, and the fuel off-gas, which is a hydrogen-containing gas, is supplied to the gas-liquid separator 36 from the anode flow path 59.

[0053] In practice, some of the water produced by the power generation in the fuel cell stack 18 moves from the cathode flow channel 58 to the anode flow channel 59 by reverse diffusion (permeation) through the membrane electrode assembly 52 . If this back-diffused water cannot be properly drained from the fuel off-gas discharge flow path 74 or the circulation flow path 77, the water will penetrate into the anode electrode 57 of the fuel cell stack 18 and block the anode flow path (fuel gas flow path) 59, causing a deterioration in the power generation stability of the fuel cell stack 18.

[0054] To prevent this inconvenience, the gas-liquid separator 36, which temporarily stores water, separates the fuel off-gas into a gas component and a liquid component (liquid water).

[0055] The gas component of the fuel off-gas (fuel off-gas) is discharged from the gas discharge port 152 of the gas-liquid separator 36 and supplied to the suction port of the ejector 34 through the circulation flow path 77.

[0056] The liquid component (liquid water) of the fuel off-gas, which consists of back-diffused water, passes from the liquid outlet 160 of the gas-liquid separator 36 through a drain flow path 162 equipped with a drain valve 164, mixes with the exhaust gas discharged from the exhaust flow path 64, and is discharged to the outside air through the exhaust flow path 99 and the exhaust gas exhaust port 168.

[0057] A portion of the fuel off-gas (hydrogen-containing gas) is discharged together with the liquid water to the drain flow path 162. After the liquid water has been discharged, only the fuel off-gas (hydrogen-containing gas) is discharged to the drain flow path 162.

[0058] In order to dilute the hydrogen gas in the fuel off-gas and discharge it to the outside, a portion of the oxidant gas discharged from the air pump 28 is supplied to the discharge flow path 64 through a bypass flow path 66 .

[0059] If the drain valve 164 continues to be open even after the water has been drained from the drain passage 162, hydrogen will be wasted. To avoid wasting hydrogen, it is necessary to close the drain valve 164 appropriately after the water has been drained from the gas-liquid separator 36.

[0060] The oxidant off-gas (including the remaining unreacted fuel off-gas) flowing through the oxidant off-gas discharge flow path 63 is mixed with the oxidant gas supplied through the oxidant gas bypass flow path 66, and then flows into the discharge flow path 64.

[0061] The discharge flow path 64 communicates with the drain flow path 162 and merges with it to communicate with the discharge flow path 99 . In the exhaust flow path 99, the fuel gas in the mixed fluid of liquid water and fuel off-gas discharged from the drain flow path 162 is diluted by the oxidant off-gas from the exhaust flow path 64, and is discharged outside the fuel cell vehicle 12 (to the atmosphere) through the exhaust gas outlet 168.

[0062] The fuel cell heat medium supply device 26 of the fuel cell system 10 has a fuel cell heat medium flow path 138 that circulates a heat medium (coolant) through a heat medium flow path 60 in the fuel cell stack 18. In addition to the heat medium flow path 60, the fuel cell heat medium flow path 138 is made up of a heat medium discharge flow path 134, a heat medium supply flow path 135, a heat medium bypass flow path 136, a heat medium discharge flow path 137, a thermo valve 37, heat medium supply flow paths 139, 140, 141, and a heat medium pump 38.

[0063] A radiator 39 for cooling the heat medium is connected between the outlet side of the heat medium supply passage 135 and the inlet side of the heat medium discharge passage 137 .

[0064] The radiator 39 cools the heat medium. The heat medium pump circulates the heat medium in the heat medium flow path 138 for the fuel cell.

[0065] A temperature sensor 76 is provided in the heat medium discharge flow path 134. A temperature sensor 79 is also provided in the heat medium supply flow path 141. In this embodiment, the temperature sensor 79 is referred to as a heat medium temperature sensor 79 for a fuel cell.

[0066] When the temperature of the heat medium flowing through the heat medium bypass flow path 136 reaches or exceeds a predetermined temperature, the thermostatic valve 37 is switched to block the heat medium bypass flow path 136, and the heat medium is discarded by the radiator 39. When the temperature of the heat medium in the heat medium bypass flow path 136 is below a predetermined temperature, the thermostatic valve 37 is switched to open the heat medium bypass flow path 136, and the heat medium flowing through the heat medium discharge flow path 134 is not cooled by the radiator 39.

[0067] The above-mentioned components of the fuel cell system 10 are controlled by a control device 15. The inlet-side sealing valve 118, the outlet-side sealing valve 120, the drain valve 164 and the switching valve 85 are flow rate adjusting valves whose valve opening is controlled by the control device 15, but they may also be duty controlled using electromagnetically controlled opening / closing valves.

[0068] The control device 15 is configured by an ECU (Electronic Control Unit). The ECU is configured by a computer having one or more processors (CPUs), a memory, an input / output interface, and an electronic circuit. The one or more processors (CPUs) execute programs (computer-executable instructions) (not shown) stored in the memory.

[0069] The processor of the control device 15 controls the operation of the fuel cell vehicle 12 and the fuel cell system 10 by executing calculations in accordance with the program. Furthermore, the control device 15 functions as a regenerative power consumption (waste electricity) control unit 200 by executing the program.

[0070] A power switch (power SW) 71 of the fuel cell vehicle 12 is connected to the control device 15. The power switch 71 is operated by a user to start or continue (ON) or end (OFF) the power generation operation of the fuel cell stack 18 of the fuel cell system 10.

[0071] An accelerator opening sensor and a vehicle speed sensor (not shown) are also connected to the control device 15. The power supply SW71 is capable of so-called RTC activation (automatic on / off) of the fuel cell system 10 using a timer (not shown).

[0072] 2 shows a regenerative power consumption system 220 including a detailed configuration of a regenerative power consumption control unit 200. The regenerative power consumption control unit 200 controls the operations of the air pump 28, the heater 82, the fuel cell heat medium supply device 26, and the heater heat medium supply device 27 to efficiently consume the regenerative power.

[0073] The regenerative power consumption control unit 200 is made up of a power consumption request control unit 202 , a heater power consumption control unit 204 , an air pump power consumption control unit 206 , a switching valve control unit 208 , an FC temperature monitoring unit 210 , and a heater temperature monitoring unit 212 .

[0074] A high voltage Vinv is applied to a power input terminal of the heater 82, and a ground terminal of the heater 82 is grounded via a switch 87. When the switch 87 is closed by the heater power consumption control unit 204, the heater 82 generates heat by a current supplied from the high voltage Vinv, which is a regenerative voltage. As the heater 82 generates heat, regenerative power is consumed and the temperature of the heater heat medium Ch rises. During heating, the heater 82 also generates heat by a current supplied from the high voltage Vbh of the power storage device 44.

[0075] [Operation] [Flowchart explanation] The fuel cell system 10 according to this embodiment is basically configured as described above. The operation of the fuel cell system 10 relating to the power consumption control of the regenerative power of the motor 46 will now be described with reference to the flowchart of FIG.

[0076] In step S1, the control device 15 determines whether the power switch 71 is in the on or off state, and if the power switch 71 remains in the off state or has been changed from the on state to the off state (step S1: NO), the process proceeds to step S2. In step S2, the control device 15 performs a process to end power generation.

[0077] On the other hand, if the power switch 71 remains on or has been changed from an off state to an on state (step S1: YES), the control device 15 advances the process to step S3.

[0078] In this embodiment, in step S1, the power switch 71 of the fuel cell vehicle 12 equipped with the fuel cell system 10 is turned on (step S1: YES) after charging while parked at a cottage (high altitude) on the top of a mountain.

[0079] After this, the fuel cell vehicle 12 is now in a downhill state, descending from the high ground mainly in so-called EV (Electric Vehicle) driving mode while applying regenerative braking without depressing the accelerator pedal. EV driving refers to a driving state in which the motor 46 is driven solely by the power of the power storage device 44.

[0080] During this downhill slope, the fuel cell system 10 is either in a power generation stop state with fuel gas shut off or in an idle power generation state with very low power to avoid deterioration due to the open circuit voltage Vocv.

[0081] In step S3, the control device 15 determines whether or not regenerative power is being generated by the motor 46.

[0082] 4 shows the current-voltage characteristic 201 of the fuel cell stack 18. The horizontal axis represents the generated current Ifc [A], and the vertical axis represents the generated voltage Vfc [V].

[0083] The fuel cell vehicle 12 performs normal driving, such as driving on flat ground, at a normal generation voltage Vn [V] where the generation voltage Vfc remains substantially constant in response to increases and decreases in the generation current Ifc. While driving downhill, the fuel cell stack 18 maintains a slight power generation state, a so-called idle power generation state, at an idle current Ifcidle (idle voltage Vfcidle). While this idle power generation state is maintained, the temperature of the fuel cell stack 18 is detected.

[0084] In this embodiment, the temperature of the fuel cell stack 18 is detected by a fuel cell heat medium temperature sensor 79 provided at the heat medium supply port to the fuel cell stack 18, and is acquired as the fuel cell heat medium temperature Tfc by the FC temperature monitoring unit 210.

[0085] In the idling power generation state, including the rise in the outside air temperature from the high ground to the low ground, the fuel cell heat medium temperature Tfc gradually rises.

[0086] While descending the slope and with the accelerator pedal not depressed, the motor 46 generates a braking force (regenerative braking force) and regenerative power. The determination in step S3 by the control device 15 is affirmative (step S3: YES), and the control device 15 proceeds with the process to step S4.

[0087] In step S4, the control device 15 acquires the SOC of the power storage device 44 by the SOC sensor 49, and determines whether or not the acquired SOC is less than the full charge threshold SOCth.

[0088] When the SOC is less than the full charge threshold SOCth (step S4: YES, SOC < SOCth), the control device 15 proceeds with the process to step S5. When the SOC is greater than or equal to the full charge threshold SOCth (step S4: NO, SOC ≥ SOCth), the control device 15 proceeds with the process to step S6.

[0089] In step S5, the control device 15 converts the regenerative power of the motor 46 into regenerative power of a high voltage Vinv via the inverter 45 and the DC / DC converter 41. The control device 15降压 the high voltage Vinv to a high voltage Vbh by the DC / DC converter 41, charges the power storage device 44 with the regenerative power that has become the high voltage Vbh, and proceeds with the process to step S1.

[0090] If the storage device 44 cannot be charged, in step S6, the power consumption request control unit 202 of the control device 15 monitors whether the heat medium temperature (referred to as the fuel cell heat medium temperature Tfc) measured by the temperature sensor 79 and monitored by the FC temperature monitoring unit 210 is equal to or higher than the first threshold temperature Th1.

[0091] In the initial state of downhill driving from high altitude, the fuel cell stack 18 is cold, so the determination in step S6 is negative (step S6: NO, the fuel cell heat medium temperature Tfc is less than the first threshold temperature Th1), and the control device 15 proceeds to step S7.

[0092] In step S7, the power consumption request control unit 202 of the control device 15 determines whether the temperature difference (differential temperature) (Tht-Tfc) obtained by subtracting the fuel cell heat medium temperature Tfc from the heat medium temperature (heater heat medium temperature Tht) measured by the temperature sensor 83 monitored by the heater temperature monitoring unit 212 is equal to or greater than the threshold temperature difference (differential threshold temperature) ΔTth.

[0093] In the initial state of downhill driving from high altitude, the heater 82 is also cold, so the determination in step S7 is negative {(Tht-Tfc)<ΔTth, (step S7: NO)}, and the control device 15 proceeds to step S8 (first power consumption control).

[0094] In step S8, heater temperature monitoring unit 212 sends an operation instruction for switching valve 85 to switching valve control unit 208. Also, in step S8, power consumption request control unit 202 may instruct heater power consumption control unit 204 to issue a heater power consumption request.

[0095] In response to the operation instruction, the switching valve control unit 208 switches the switching valve 85 to the shutoff state.

[0096] In response to the heater power consumption request instruction, the heater power consumption control unit 204 energizes the heater 82. In the energized state, the heater 82 generates heat using the regenerated power of the high voltage Vinv.

[0097] FIG. 5A shows the flow paths of the heat mediums Cf and Ch when the switching valve 85 is switched to the shutoff state (a state in which the fuel cell heat medium Cf and the heater heat medium Ch are shut off) (during the processing of step S8).

[0098] Since the heater heat medium Ch circulates within the heater heat medium supply device 27, the temperature Tht of the heater heat medium Ch gradually rises in accordance with the power consumption of the regenerative power by the heater 82 based on the control of the heater power consumption control unit 204.

[0099] The power consumption control of the regenerative power in step S8 is referred to as first power consumption control or heater-only power consumption control. After the processing of step S8, the heater heat medium temperature Tht rises during the first power consumption control of step S8 after step S1: YES, step S3: YES, step S4: NO, step S6: NO, and step S7: NO. When the heater heat medium temperature Tht rises and the determination of step S7 is affirmative {(Tht-Tfc)≧ΔTth, (step S7: YES)}, the control device 15 proceeds to the processing of step S9.

[0100] If the determination in step S7 is affirmative, the control device 15 may limit the power consumption of the regenerative power in the heater 82 (heater heat medium supply device 27) so that the heater heat medium temperature Tht does not rise any further.

[0101] In step S9, heater temperature monitoring unit 212 of regenerative power consumption control unit 200 sends an operation instruction to switching valve control unit 208 to put switching valve 85 into a communicating state. Furthermore, in step S9, power consumption request control unit 202 sends waste heat recovery permission information to switching valve control unit 208 based on the waste heat recovery permission information from FC temperature monitoring unit 210 (step S7: YES).

[0102] The switching valve control unit 208 switches the switching valve 85 from a shutoff state to a communication state (a state in which the fuel cell heat medium Cf and the heater heat medium Ch are in communication) based on the waste heat recovery permission information and the operation instruction. When the switching valve 85 is in the communication state, the valve opening of the switching valve 85 may be adjusted to an intermediate opening between a fully open state and a closed state.

[0103] FIG. 5B shows the flow paths of the heat transfer media Cf and Ch when the switching valve 85 is switched to the communicating state (during the processing of step S9).

[0104] The heater heat medium Ch flowing through the flow path 144 of the heater heat medium supply device 27 passes through the switching valve 85, merges with the fuel cell heat medium Cf flowing through the flow path 140, and is introduced into the fuel cell stack 18 via the flow path 141.

[0105] By processing step S9, the waste heat of the heater heat medium Ch, whose temperature has been increased by the heater 82, is transferred to the fuel cell heat medium Cf, thereby increasing the temperature of the fuel cell stack 18 and putting the fuel cell stack 18 into a waste heat recovery state. The power consumption control of the regenerative power in step S9 is referred to as second power consumption control or heater-fuel cell combined power consumption control.

[0106] When the waste heat recovery state is entered by performing the process of step S9, the temperature of the fuel cell stack 18, i.e., the fuel cell heat medium temperature Tfc, increases at a faster rate, while the heater heat medium temperature Tht decreases slowly.

[0107] Therefore, after the processing of step S9, the processing of step S1: YES, step S3: YES, step S4: NO, step S6: NO, step S7: YES, and step S9 is repeated. During the repetition of this process, the switching valve control unit 208 may adjust the communication opening degree (valve opening degree) of the switching valve 85 based on the fuel cell heat medium temperature Tfc monitored by the FC temperature monitoring unit 210 and the heater heat medium temperature Tht monitored by the heater temperature monitoring unit 212 so as to satisfy the conditional equation (Tht-Tfc≧ΔTth) in step S7.

[0108] During the repetition of this process, when the fuel cell heat medium temperature Tfc of the fuel cell stack 18 rises and the judgment in step S6 becomes positive (Tfc≧Th1, step S6: YES), the control device 15 (power consumption request control unit 202 of the regenerative power consumption control unit 200) proceeds to step S10.

[0109] In step S10, the FC temperature monitoring unit 210 of the regenerative power consumption control unit 200 sends an operation instruction to the switching valve control unit 208 to change the switching valve 85 from a connected state to a blocked state, and also sends air pump power consumption permission information (AP power consumption permission information) to the power consumption request control unit 202. In step S10, power consumption request control unit 202 withdraws the heater power consumption request to heater power consumption control unit 204. It also withdraws the waste heat recovery permission information to switching valve control unit 208. Furthermore, power consumption request control unit 202 sends an air pump power consumption request to air pump power consumption control unit 206. In step S10, the air pump power consumption control unit 206 increases the rotation speed of the air pump 28 to a predetermined rotation speed and opens the bypass valve 122 to prevent excessive supply of oxidant gas from the air pump 28 to the fuel cell stack 18. In step S10, the regenerative power of the motor 46 is consumed by the air pump 28. The power consumption control of the regenerative power in step S10 is referred to as third power consumption control or air pump only power consumption control.

[0110] After the processing of step S10, while the processing of step S1: YES, step S3: YES, step S4: NO, step S6: YES, and step S10 is repeated, the fuel cell vehicle 12 ends downhill traveling. When downhill traveling ends and the vehicle switches to traveling on flat ground, for example, the determination of step S3 becomes negative (step S3: NO), and the fuel cell system 10 of the fuel cell vehicle 12 ends the power consumption control of the regenerative power.

[0111] During the regenerative power consumption control (third power consumption control) in step S10, in order to maintain the fuel cell heat medium temperature Tfc at a constant first threshold temperature Th1, the valve opening of the thermo valve 37 may be adjusted and cooling of the fuel cell heat medium Cf by the radiator 39 may be used in combination.

[0112] For ease of understanding, FIG. 6 shows an explanatory table 250 for the power consumption control of regenerative power (including the control of the switching valve 85) in steps S8 to S10 described with reference to the flowchart of FIG.

[0113] [Explanation using timing chart] An example of the operation described with reference to the flowchart in FIG. 3 will now be described with reference to the timing chart in FIG.

[0114] The AP power consumption request in Figure 7 (shown third from the top in Figure 7) is a request for the regenerative power to be consumed by the air pump 28, and the heater power consumption request (shown fourth from the top in Figure 7) is a request for the regenerative power to be consumed by the heater 82.

[0115] The regenerated power may be consumed directly by the auxiliary devices without going through the power storage device 44. Alternatively, the regenerated power may be consumed by repeatedly charging and discharging the power storage device 44 while supplying power to the auxiliary devices so that the power storage device 44 does not exceed the full charge threshold SOCth. In either case, the consumption of regenerated power is determined.

[0116] At time t0, the power switch 71 (shown in the top row in FIG. 7) transitions from the off state to the on state (step S1: YES). At time t0, a power consumption request (shown in the second row from the top in FIG. 7) for regenerative power (step S3: YES) occurs as the fuel cell vehicle 12 goes downhill, and at the same time, the power consumption request control unit 202 issues the heater power consumption request to the heater power consumption control unit 204.

[0117] At time t0, the heater 82 is energized while the switching valve 85 remains in the shutoff state, and consumption of the regenerated power is started (step S8, FIG. 5A, first power consumption control). At time t0, the fuel cell system 10 starts a standby or idling power generation state in which power generation is stopped. At time t0, the fuel cell vehicle 12 equipped with the fuel cell system 10 starts to travel downhill in EV running using the motor 46.

[0118] When traveling downhill, the heater 82 consumes the regenerative power generated by the motor 46 (first power consumption control by the heater alone), causing the heater heat medium temperature Tht (shown at the bottom in Figure 7) to start rising from time t0.

[0119] At time t1, when the temperature difference (Tht-Tfc) obtained by subtracting the fuel cell heat medium temperature Tfc (shown third from the bottom in Figure 7) from the heater heat medium temperature Tht becomes equal to or greater than the threshold temperature difference ΔTth {(Tht-Tfc)≧ΔTth}, waste heat recovery permission information is sent from the power consumption request control unit 202 to the switching valve control unit 208.

[0120] Transforming the inequality {(Tht-Tfc)≧ΔTth} into {Tht≧(Tfc+ΔTth)}, in other words, when the heater heat medium temperature Tht becomes equal to or higher than the temperature obtained by adding the fuel cell heat medium temperature Tfc to the threshold temperature difference ΔTth (time t1), the power consumption request control unit 202 sends waste heat recovery permission information to the switching valve control unit 208.

[0121] Based on the waste heat recovery permission information, the switching valve control unit 208 issues a switching valve operation instruction (shown second from the bottom in Figure 7), and between time t1 and time t2, the switching valve 85 is brought into a communicating state (Figure 5B), and the waste heat generated by the heater 82 is recovered by the fuel cell stack 18 (step S9, Figure 5B, second power consumption control by heater-fuel cell cooperation).

[0122] Therefore, as shown in the third graph from the bottom in FIG. 7, the rate of increase in the fuel cell heat medium temperature Tfc increases between time t1 and time t2.

[0123] At time t2, the fuel cell heat medium temperature Tfc reaches the first threshold temperature Th1 (step S6: YES). At time t2, the air pump power consumption permission information (shown fourth from the bottom in FIG. 7) changes from "No" to "Yes." After time t2, the fuel cell heat medium temperature Tfc is controlled to a constant value, the first threshold temperature Th1.

[0124] As a result, at time t3, power consumption request control unit 202 issues an air pump power consumption request to air pump power consumption control unit 206, and at the same time, the heater power consumption request is withdrawn. From time t4, the rotation speed of air pump 28 (shown fifth from the top in FIG. 7) is increased to a predetermined rotation speed to start consuming regenerative power (step S10, third power consumption control using only the air pump).

[0125] At time t6, for example, when the fuel cell vehicle 12 comes from a downhill slope onto flat ground and starts parking on the flat ground, the motor 46 does not generate regenerative power (step S3: NO). At time t6, the power consumption request control unit 202 cancels the air pump power consumption request. After time t6, the fuel cell system 10 is put into an idle power generation state.

[0126] [Note] In addition to the above disclosure, the following additional notes are disclosed. (Supplementary Note 1) A fuel cell system 10 includes a fuel cell 18 that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas supplied from an air pump 28, a fuel cell heat medium supply device 26 that supplies a heat medium to the fuel cell that controls the temperature of the fuel cell, a fuel cell heat medium temperature sensor 79 that detects the temperature of the heat medium that controls the temperature of the fuel cell, a heater heat medium supply device 27 that branches the heat medium and supplies it to a heater 82, a heater heat medium temperature sensor 83 that detects the temperature of the heat medium that controls the temperature of the heater, and a switching valve 85 that connects or disconnects the heat medium flowing through the fuel cell heat medium supply device and the heat medium flowing through the heater heat medium supply device, and the air pump, the fuel cell, and the oxidant gas are supplied from at least one of an electricity storage device 44 and the fuel cell. a fuel cell system that supplies auxiliary electric power to a fuel cell heat medium supply device and a heater heat medium supply device, and also supplies driving electric power to generate driving force to a motor (46), and when the regenerative electric power generated in the motor cannot be charged to the power storage device, if the fuel cell heat medium temperature is less than a first threshold temperature (Th1) and the temperature difference (Tht-Tfc) obtained by subtracting the fuel cell heat medium temperature from the heater heat medium temperature is equal to or greater than a threshold temperature difference (ΔTth), the switching valve is switched to a communicating state to increase the fuel cell heat medium temperature, and if the fuel cell heat medium temperature is equal to or greater than the first threshold temperature, the switching valve is switched to a blocking state to increase the rotation speed of the air pump so that the regenerative electric power is consumed by the air pump, performing power consumption control.

[0127] In this way, when regenerative power is generated in the motor but cannot be charged to the storage device, the regenerative power is consumed in the following order: heater alone, heater-fuel cell combination, and air pump alone. This allows the regenerative power to be consumed appropriately without freezing the fuel cell system.

[0128] In other words, when regenerative power is being generated, power generation by the fuel cell is in an idle state and the stack temperature is low. If the air pump is rotated at high speed (normal rotation) using regenerative power when the stack temperature is low, the fuel cell system may freeze.

[0129] In contrast, in this invention, by providing a period in which the heater consumes regenerative power alone and a period in which the heater and fuel cell consume regenerative power in cooperation before the air pump consumes regenerative power alone, it is possible to accurately control the temperature of the fuel cell and ensure that the regenerative power is consumed, thereby contributing to energy efficiency.

[0130] (Appendix 2) In the fuel cell system described in Appendix 1, when the fuel cell heat medium temperature is lower than the first threshold temperature, the power consumption control is not performed, which increases the rotation speed of the air pump to cause the air pump to consume the regenerative power. This makes it possible to reliably prevent the fuel cell from freezing.

[0131] (Appendix 3) In the fuel cell system described in Appendix 1, when the regenerative power generated in the motor cannot be charged to the power storage device, if the fuel cell heat medium temperature is less than the first threshold temperature and the temperature difference obtained by subtracting the fuel cell heat medium temperature from the heater heat medium temperature is less than the threshold temperature difference, a first power consumption control is performed in which the switching valve is set to a shut-off state and the regenerative power is supplied to the heater to be consumed.

[0132] In this way, when regenerative power is generated in the motor and the regenerative power cannot be charged to the storage device, if the temperature of the heat medium for the fuel cell is less than a first threshold temperature and the temperature difference obtained by subtracting the heat medium temperature for the heater from the heat medium temperature for the fuel cell is less than a threshold temperature difference, a first power consumption control is performed in which the switching valve is set to a shut-off state and the regenerative power is consumed by the heater alone.

[0133] When regenerative power is being generated, power generation by the fuel cell is in an idle state, and the stack temperature is low. If the air pump is rotated at high speed (normal rotation) using regenerative power when the stack temperature is low, the fuel cell system may freeze. In contrast, during this first power consumption control, the heater alone consumes regenerative power, so the temperature of the fuel cell can be accurately controlled and the regenerative power can be reliably consumed. This ultimately contributes to energy efficiency.

[0134] (Appendix 4) In the fuel cell system described in Appendix 3, during the first power consumption control in which the regenerative power is supplied to the heater and consumed, when the temperature of the heat medium for the fuel cell is less than the first threshold temperature and the temperature difference obtained by subtracting the heat medium temperature for the fuel cell from the heat medium temperature for the heater is equal to or greater than the threshold temperature difference, the switching valve is switched to a communicating state, and the regenerative power is supplied to the heater and consumed while the temperature of the heat medium for the fuel cell is raised, and the waste heat of the heater is recovered by the fuel cell and the fuel cell is heated.

[0135] In this way, a second power consumption control is performed in which the regenerative power is consumed by the heater and the heater heat medium heated by the heater is merged with the fuel cell heat medium to recover heat in the fuel cell, thereby making it possible to increase the temperature of the fuel cell while avoiding freezing of the fuel cell system.

[0136] (Supplementary Note 5) In the fuel cell system according to Supplementary Note 1, when the switching valve is in a communicating state, the valve opening degree of the switching valve is adjusted to an intermediate opening degree between a fully open state and a closed state.

[0137] In this way, by adjusting the valve opening of the switching valve when the switching valve is in a communicating state, the waste heat of the heater heat medium can be accurately recovered by the fuel cell (heat medium for the fuel cell).

[0138] (Appendix 6) In the fuel cell system described in Appendix 1 or 2, when the fuel cell heat medium temperature becomes equal to or higher than the first threshold temperature, a third power consumption control is performed in which the switching valve is switched to a shut-off state to stop power consumption by the heater, and the rotation speed of the air pump is increased to cause the regenerative power to be consumed by the air pump.

[0139] In this way, since the fuel cell heat medium temperature is equal to or higher than the first threshold temperature, in other words, the fuel cell temperature is relatively high and the fuel cell side is warmed up, freezing of the fuel cell system can be avoided even if the air pump rotation speed is increased. Also, the regenerative power can be reliably consumed by the air pump. In this case, the heater can be operated as a heating air conditioner independently of the fuel cell.

[0140] (Supplementary Note 7) In the fuel cell system described in Supplementary Note 1, the regenerative power is generated in the motor when the fuel cell system is traveling downhill and a braking force is generated by the motor.

[0141] This allows the regenerative power generated by the motor when the fuel cell system is going downhill to be consumed by the heater, or the heater and the heat medium for the fuel cell, or the air pump, thereby ensuring the generation of braking force when going downhill and preventing the fuel cell from overcooling.

[0142] The present disclosure is not limited to the above disclosure, and various configurations may be adopted without departing from the gist of the present disclosure.

[0143] For example, in the above disclosure, an operation instruction is sent to the switching valve control unit 208 from the heater temperature monitoring unit 212 provided in the regenerative power consumption control unit 200, but the switching valve 85 may also be controlled via another different control unit based on the waste heat recovery permission information. [Explanation of symbols]

[0144] 10...Fuel cell system 12...Fuel cell vehicle 15...Control device 16...Output unit 18... fuel cell stack (fuel cell) 26... fuel cell heat medium supply device 27... Heating medium supply device for heater 28... Air pump 44...electricity storage device 46...motor 79...Heat medium temperature sensor for fuel cell (temperature sensor) 82...Heater 83...Heater heat medium temperature sensor (temperature sensor) 84...Heater core 85...Switching valve 200...Regenerative power consumption control unit (control unit)

Claims

1. a fuel cell that generates electricity through an electrochemical reaction between fuel gas and oxidant gas supplied from an air pump; a fuel cell heat medium supply device that supplies a heat medium to the fuel cell to control the temperature of the fuel cell; a fuel cell heat medium temperature sensor for detecting the temperature of the heat medium for controlling the temperature of the fuel cell; a heater heat medium supply device that branches the heat medium and supplies it to the heater; a heater heat medium temperature sensor for detecting the temperature of a heat medium for controlling the temperature of the heater; a switching valve for connecting or blocking the heat medium flowing through the fuel cell heat medium supply device and the heat medium flowing through the heater heat medium supply device, a fuel cell system that supplies auxiliary power to the air pump, the fuel cell heat medium supply device, and the heater heat medium supply device, and also supplies driving power to a motor to generate driving force, from at least one of a power storage device and the fuel cell, When the regenerative electric power generated in the motor cannot be charged to the power storage device, if the temperature of the heat medium for the fuel cell is lower than a first threshold temperature and the temperature difference obtained by subtracting the temperature of the heat medium for the fuel cell from the temperature of the heat medium for the heater is equal to or greater than a threshold temperature difference, the switching valve is switched to a communicating state to increase the temperature of the heat medium for the fuel cell, When the temperature of the heat medium for the fuel cell becomes equal to or higher than the first threshold temperature, the switching valve is switched to a shutoff state, and the rotation speed of the air pump is increased to perform power consumption control in which the regenerative power is consumed by the air pump. Fuel cell system.

2. 2. The fuel cell system according to claim 1, When the fuel cell heat medium temperature is lower than the first threshold temperature, the power consumption control for increasing the rotation speed of the air pump to consume the regenerative power by the air pump is not performed. Fuel cell system.

3. 2. The fuel cell system according to claim 1, When the regenerative power generated in the motor cannot be charged to the power storage device, if the temperature of the heat medium for the fuel cell is less than the first threshold temperature and the temperature difference obtained by subtracting the temperature of the heat medium for the fuel cell from the temperature of the heat medium for the heater is less than the threshold temperature difference, a first power consumption control is performed in which the switching valve is brought into a shutoff state and the regenerative power is supplied to the heater to be consumed. Fuel cell system.

4. 4. The fuel cell system according to claim 3, During the first power consumption control in which the regenerative power is supplied to the heater and consumed, when the temperature of the heat medium for the fuel cell is lower than the first threshold temperature and the temperature difference obtained by subtracting the temperature of the heat medium for the fuel cell from the temperature of the heat medium for the heater becomes equal to or greater than the threshold temperature difference, the switching valve is switched to a communicating state, and the regenerative power is supplied to the heater and consumed, while the temperature of the heat medium for the fuel cell is increased, and waste heat of the heater is recovered by the fuel cell to heat the fuel cell. Fuel cell system.

5. 2. The fuel cell system according to claim 1, When the switching valve is in a communicating state, the valve opening degree of the switching valve is adjusted to an intermediate opening degree between a fully open state and a closed state. Fuel cell system.

6. 2. The fuel cell system according to claim 1, When the temperature of the heat medium for the fuel cell becomes equal to or higher than the first threshold temperature, the switching valve is switched to a shutoff state to stop power consumption by the heater, and the rotation speed of the air pump is increased to cause the regenerative power to be consumed by the air pump, thereby performing third power consumption control. Fuel cell system.

7. 2. The fuel cell system according to claim 1, The regenerative power is generated in the motor when a braking force is generated by the motor while the fuel cell system is descending a slope. Fuel cell system.

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