JP7124751B2 - fuel cell system - Google Patents

Description

The present invention relates to fuel cell systems.

In a fuel cell system, for example, as described in Patent Document 1, when starting below freezing, the cathode gas (for example, , air) is known to generate power at low efficiency and to warm up the fuel cell stack.

JP-A-2004-30979

The fuel cell system may perform warm-up operation until the output of the fuel cell stack is ensured even when the temperature of the fuel cell stack rises to a level where the fuel cell stack does not freeze. In this case, the operating noise continues to be generated from the auxiliary parts, and even if the user requires quietness, a situation may arise in which quietness cannot be ensured.

The present invention has been made to solve the above problems, and can be implemented as the following modes.

According to one aspect of the present invention, there is provided a fuel cell system that performs warm-up operation having a normal warm-up operation mode and a low-speed warm-up operation mode. This fuel cell system includes a fuel cell stack, a compressor that supplies a cathode gas to the fuel cell stack, a temperature measuring unit that obtains a stack temperature of the fuel cell stack, and a stack temperature that is set in advance during the warm-up operation. A control unit that controls the output voltage of the fuel cell stack to a predetermined voltage and the cathode gas supply amount of the compressor to a predetermined supply amount until the temperature rises to a predetermined first threshold temperature. and, when the normal warm-up operation mode of the warm-up operation is selected, the stack temperature is from the first threshold temperature to a second threshold higher than the first threshold temperature Until the temperature rises, the output voltage of the fuel cell stack is controlled to a predetermined first voltage, and the cathode gas supply amount of the compressor is controlled to a predetermined first supply amount, and the warm-up When the low-speed warm-up mode of operation is selected, the output voltage of the fuel cell stack is increased from the first voltage until the stack temperature rises from the first threshold temperature to the second threshold temperature. obtaining a request to control to a high second voltage, control the cathode gas supply amount of the compressor to a second supply amount smaller than the first supply amount, obtain a request to end the warm-up operation, and obtain the stack temperature is equal to or higher than the first threshold temperature, the warm-up operation is terminated. According to the fuel cell system of this aspect, when the low-speed warm-up operation mode is selected, the output voltage of the fuel cell stack is normally warmed up until the stack temperature rises from the first threshold temperature to the second threshold temperature. Since the second voltage is controlled to be higher than the voltage in the operation mode, and the cathode gas supply amount of the compressor is controlled to be the second supply amount smaller than the supply amount in the normal warm-up operation mode, operation noise can be reduced. Also, when a request to end the warm-up operation is acquired and the stack temperature is equal to or higher than the first threshold temperature, the warm-up operation is ended. Therefore, quietness can be ensured according to the user's request.

It should be noted that the present invention can be implemented in various forms, such as a power generation device including a fuel cell system, a vehicle including a fuel cell system, a control method for a fuel cell system, and the like. is.

1 is a diagram showing a schematic configuration of a fuel cell system; FIG. 4 is a flow chart showing an example of a warm-up operation procedure; 4 is a timing chart showing an example of stack temperature during warm-up operation; 4 is a graph showing the relationship between current, voltage, and cathode gas supply amount.

A. First embodiment:
FIG. 1 is a diagram showing a schematic configuration of a fuel cell system 100 according to one embodiment of the invention. The fuel cell system 100 includes a fuel cell stack 10 , a control section 20 , a cathode gas supply section 30 , an anode gas supply section 50 and a cooling medium circulation section 70 . The fuel cell system 100 also includes a DC/DC converter 80 , a power control unit (hereinafter referred to as “PCU”) 81 , a load 82 , a voltage detector 83 and an ammeter 84 . The fuel cell system 100 of this embodiment is mounted on, for example, a fuel cell vehicle.

The fuel cell stack 10 is a polymer electrolyte fuel cell that generates electricity by receiving supply of an anode gas (eg, hydrogen gas) and a cathode gas (eg, air) as reaction gases. The fuel cell stack 10 is configured by stacking a plurality of fuel cells 11 . Each fuel cell 11 includes a membrane electrode assembly (not shown) in which an anode (not shown) and a cathode (not shown) are arranged on both sides of an electrolyte membrane (not shown), and a membrane electrode assembly. and a pair of sandwiching separators (not shown).

The control unit 20 is configured as a computer including a CPU, a memory, and an interface circuit to which components described later are connected. The control unit 20 outputs signals for controlling start and stop of each device in the fuel cell stack 10 according to instructions from an ECU (Electronic Control Unit) 22 and an instruction input unit 23 . By executing the control program stored in the memory, the control unit 20 controls the power generation by the fuel cell system 100 and also implements a warm-up operation process to be described later. In this embodiment, the warm-up operation has a normal warm-up operation mode and a low-speed warm-up operation mode. The low-speed warm-up operation mode is a warm-up operation mode in which the temperature of the fuel cell stack 10 rises more slowly than in the normal warm-up operation mode. In addition, the control part 20 may implement|achieve a part or all of these controls by a hardware circuit.

The ECU 22 is a control unit that controls the entire device (for example, a vehicle) including the fuel cell system 100 . For example, in a fuel cell vehicle, the ECU 22 controls the vehicle according to a plurality of input values such as the amount of depression of an accelerator pedal, the amount of depression of a brake pedal, vehicle speed, and the like. Note that the ECU 22 may be included as part of the functions of the control unit 20 .

The instruction input unit 23 is an input unit that selects a mode in warm-up operation and end of warm-up operation. In this embodiment, the instruction input unit 23 is a button on the display of the car navigation system equipped with a touch sensor. Note that the instruction input unit 23 may be an existing button-type operating device.

The cathode gas supply unit 30 includes a cathode gas pipe 31 , an air flow meter 32 , a compressor 33 , a first on-off valve 34 , a flow dividing valve 36 , a cathode gas discharge pipe 41 and a first regulator 42 . The cathode gas pipe 31 is connected to the fuel cell stack 10 and supplies air taken in from the outside to the fuel cell stack 10 .

The airflow meter 32 is provided on the cathode gas pipe 31 and measures the flow rate of the air taken in. The compressor 33 compresses air taken in from the outside according to a control signal from the control unit 20 and supplies the air to the fuel cell stack 10 as cathode gas. A first on-off valve 34 is provided between the compressor 33 and the fuel cell stack 10 . The flow dividing valve 36 is provided between the compressor 33 and the cathode gas discharge pipe 41 and adjusts the flow rate of air to the fuel cell stack 10 and the cathode gas discharge pipe 41 . The flow dividing valve 36 opens and closes according to a control signal from the control section 20 .

The cathode gas discharge pipe 41 discharges the cathode gas discharged from the fuel cell stack 10 to the outside of the fuel cell system 100 . The cathode gas discharged from the fuel cell stack 10 is also called cathode off-gas. The first regulator 42 adjusts the pressure of the cathode gas outlet of the fuel cell stack 10 according to the control signal from the controller 20 .

The anode gas supply unit 50 includes an anode gas pipe 51, an anode gas tank 52, a second on-off valve 53, a second regulator 54, an injector 55, an anode gas discharge pipe 61, a gas-liquid separator 62, and an exhaust gas. A drain valve 63 , a circulation pipe 64 and an anode gas pump 65 are provided.

The anode gas tank 52 is connected to the anode gas inlet of the fuel cell stack 10 via the anode gas pipe 51 and supplies anode gas to the fuel cell stack 10 . The second on-off valve 53 , the second regulator 54 , and the injector 55 are provided in the anode gas pipe 51 in this order from the upstream side, that is, from the side closer to the anode gas tank 52 .

The second on-off valve 53 opens and closes according to a control signal from the controller 20 . The second on-off valve 53 is closed when the fuel cell system 100 is stopped. The second regulator 54 adjusts the pressure of the anode gas on the upstream side of the injector 55 according to the control signal from the controller 20 . The injector 55 is an electromagnetically driven open/close valve whose valve body is electromagnetically driven according to the drive cycle and valve opening time set by the control unit 20 . The control unit 20 controls the flow rate of the anode gas supplied to the fuel cell stack 10 by controlling the drive cycle and valve opening time of the injector 55 .

The anode gas discharge pipe 61 is a pipe that connects the anode gas outlet of the fuel cell stack 10 and the gas-liquid separator 62 . The anode gas discharge pipe 61 guides the anode off-gas containing hydrogen gas, nitrogen gas, etc., which has not been used in the power generation reaction, to the gas-liquid separator 62 .

The gas-liquid separator 62 is connected between the anode gas discharge pipe 61 and the circulation pipe 64 of the circulation passage 66 . The gas-liquid separator 62 separates water as an impurity from the anode off-gas in the circulation flow path 66 and stores the water.

The exhaust/drain valve 63 is provided below the gas-liquid separator 62 . The exhaust drain valve 63 drains water stored in the gas-liquid separator 62 and exhausts unnecessary gas (mainly nitrogen gas) in the gas-liquid separator 62 . During operation of the fuel cell system 100 , the exhaust/drain valve 63 is normally closed and opens and closes according to a control signal from the controller 20 . In this embodiment, the exhaust/drain valve 63 is connected to the cathode gas discharge pipe 41 , and the water and unnecessary gas discharged by the exhaust/drain valve 63 are discharged to the outside through the cathode gas discharge pipe 41 .

The circulation pipe 64 is connected to a portion of the anode gas pipe 51 downstream of the injector 55 . The circulation pipe 64 is provided with an anode gas pump 65 that is driven according to a control signal from the controller 20 . The anode off-gas from which water has been separated by the gas-liquid separator 62 is sent to the anode gas pipe 51 by the anode gas pump 65 . In this fuel cell system 100, the hydrogen-containing anode off-gas is circulated and supplied to the fuel cell stack 10 again, thereby improving the utilization efficiency of the anode gas.

The cooling medium circulation unit 70 adjusts the temperature of the fuel cell stack 10 by circulating the cooling medium through the fuel cell stack 10 . The cooling medium circulation section 70 includes a coolant supply pipe 71 , a coolant discharge pipe 72 , a radiator 73 , a coolant pump 74 , a three-way valve 75 , a bypass pipe 76 and a temperature measurement section 77 . As the coolant, for example, water, non-freezing water such as ethylene glycol, air, or the like is used.

The coolant supply pipe 71 is connected to the coolant inlet in the fuel cell stack 10 , and the coolant discharge pipe 72 is connected to the coolant outlet of the fuel cell stack 10 . The radiator 73 is connected to the coolant discharge pipe 72 and the coolant supply pipe 71 , and cools the cooling medium flowing from the coolant discharge pipe 72 by blowing air from an electric fan or the like, and then discharges it to the coolant supply pipe 71 . The coolant pump 74 is provided in the coolant supply pipe 71 and pressure-feeds the coolant to the fuel cell stack 10 . A three-way valve 75 regulates the flow rate of coolant to the radiator 73 and bypass pipe 76 . The temperature measurement unit 77 is connected to the coolant discharge pipe 72 and measures the temperature of cooling water discharged from the fuel cell stack 10 . The temperature measured by the temperature measurement unit 77 is approximately equal to the stack temperature of the fuel cell stack 10 . Therefore, the temperature measuring section 77 corresponds to a temperature measuring section that acquires the stack temperature of the fuel cell stack 10 .

DC/DC converter 80 boosts the output voltage of fuel cell stack 10 and supplies it to PCU 81 . The PCU 81 incorporates an inverter and supplies power to the load 82 via the inverter according to the control of the control unit 20 . Also, the PCU 81 limits the current of the fuel cell stack 10 under the control of the control unit 20 .

Voltage detector 83 detects the voltage of fuel cell stack 10 . In this embodiment, the voltage detector 83 calculates the average cell voltage from the voltage of the fuel cell stack 10. FIG. “Average cell voltage” is a value obtained by dividing the voltage across the fuel cell stack 10 by the number of fuel cells 11 . Ammeter 84 measures the output current value of fuel cell stack 10 .

Electric power of the fuel cell stack 10 is supplied via a power supply circuit including the PCU 81 to a load 82 such as a traction motor (not shown) for driving wheels (not shown), the compressor 33 described above, the anode gas pump 65 and It is supplied to various valves.

FIG. 2 is a flow chart showing an example of the warm-up process procedure according to the present embodiment. The warm-up process is started when the stack temperature Tfc is lower than a predetermined first threshold temperature Tth1. The first threshold temperature Tth1 is preferably a temperature at which the fuel cell stack 10 does not freeze, and can be determined by conducting experiments in advance. The first threshold temperature Tth1 is, for example, a temperature higher than 0 degrees.

First, in step S100, the control unit 20 controls the output voltage of the fuel cell stack 10 to become a predetermined first voltage, and adjusts the cathode gas supply amount supplied to the fuel cell stack 10 by the compressor 33 in advance. By controlling the fuel cell system 100 to the predetermined first supply amount, the power generation efficiency of the fuel cell system 100 is reduced, and warm-up operation is performed. The first voltage can be determined based on a map or function that defines the relationship between current and voltage. The first supply amount can be determined based on a map or function that defines the relationship between the current and the cathode gas supply amount. The relationship between voltage, current, and cathode gas supply amount will be described later.

Next, in step S110, the control unit 20 determines whether or not the stack temperature Tfc is equal to or higher than the first threshold temperature Tth1. If the stack temperature Tfc is lower than the first threshold temperature Tth1, the controller 20 repeats the process of step S110. That is, power generation at the first voltage is continued until the stack temperature Tfc rises to the first threshold temperature Tth1. On the other hand, when the stack temperature Tfc is equal to or higher than the first threshold temperature Tth1, the controller 20 proceeds to the process of step S120.

Subsequently, in step S120, the control unit 20 determines whether or not there is an end request. The end request can be obtained from the instruction input unit 23, for example. If there is a termination request, the control unit 20 terminates the warm-up process. On the other hand, if there is no termination request, the control unit 20 proceeds to the process of step S130 and determines whether or not the low-speed warm-up operation mode is selected. If the low-speed warm-up mode has not been selected, that is, if the normal warm-up mode has been selected, the controller 20 proceeds to step S150. When the low-speed warm-up operation mode is selected, the control unit 20 proceeds to the process of step S140, controls the output voltage of the fuel cell stack 10 to a second voltage higher than the first voltage, and controls the compressor 33 controls the cathode gas supply amount supplied to the fuel cell stack 10 to a second supply amount that is smaller than the first supply amount, and the fuel cell system 100 generates power.

Finally, in step S150, the control unit 20 determines whether or not the stack temperature Tfc is equal to or higher than the second threshold temperature Tth2. The second threshold temperature Tth2 is a temperature higher than the first threshold temperature Tth1, and is a temperature at which the fuel cell stack 10 can output predetermined electric power. The predetermined power is, for example, power sufficient to drive the load 82 such as a traction motor. If the stack temperature Tfc is lower than the second threshold temperature Tth2, the controller 20 repeats the process of step S150. That is, until the stack temperature Tfc rises to the second threshold temperature Tth2, power generation is continued at the first voltage and the first supply amount in the normal warm-up operation mode, and at the second voltage and the first supply amount in the low-speed warm-up operation mode. 2 Continuing power generation with supply. On the other hand, when the stack temperature Tfc is equal to or higher than the second threshold temperature Tth2, the controller 20 terminates the warm-up process.

FIG. 3 is a timing chart showing an example of stack temperature during warm-up operation. A graph G1a shows the case of the normal warm-up operation mode, and a graph G2a shows the case of the low-speed warm-up operation mode. For convenience of explanation, the graph G2a is shown shifted downward, but in reality it partially overlaps with the graph G1a, and the stack temperature Tfc at timing t3 is the second threshold temperature Tth2.

As shown in FIG. 3, during the period from timing t0 to timing t1 when the stack temperature Tfc is equal to or lower than Tth1, power is generated at the first voltage in both the normal warm-up operation mode and the low-speed warm-up operation mode. The slope of the rise in temperature Tfc is the same. In the normal warm-up operation mode indicated by the graph G1a, the stack temperature Tfc rises to the second threshold temperature Tth2 at timing t2. On the other hand, in the low-speed warm-up operation mode indicated by graph G2a, power is generated at the second voltage (>first voltage) from timing t1, so the stack temperature Tfc rises more slowly than graph G1a and later than timing t2. At timing t3, the stack temperature Tfc rises to the second threshold temperature Tth2.

FIG. 4 is a graph showing the relationship between current, voltage, and cathode gas supply amount. A graph G1b indicated by a one-dot chain line indicates the relationship between current and voltage in the normal warm-up mode, and a graph G2b indicates the relationship between current and voltage in the low-speed warm-up mode. A solid line graph G1c shows the relationship between the current and the cathode gas supply amount in the normal warm-up operation mode, and a graph G2c shows the relationship between the current and the cathode gas supply amount in the slow warm-up operation mode. .

As shown in FIG. 4, the second supply amount Q2 of the current I2 at the second voltage V2 in the low-speed warm-up mode is the first supply amount of the current I1 at the first voltage V1 in the normal warm-up mode. Less than Q1. That is, in the low-speed warm-up operation mode, the rotation speed of the compressor 33 is lower than in the normal warm-up operation mode, and the operation noise is reduced.

According to the fuel cell system 100 of the present embodiment described above, when the low-speed warm-up operation mode is selected, the control unit 20 causes the stack temperature Tfc to rise from the first threshold temperature Tth1 to the second threshold temperature Tth2. until the output voltage of the fuel cell stack 10 is controlled to the second voltage V2 higher than the first voltage V1 in the normal warm-up operation mode, and the cathode gas supply amount of the compressor 33 is controlled to the first voltage V1 in the normal warm-up operation mode. The second supply amount Q2 is controlled to be smaller than the supply amount Q1. Therefore, when the low-speed warm-up operation mode is selected, the rotation speed of the compressor 33 can be reduced more than in the normal warm-up operation mode, and the operating noise can be reduced. Also, when a request to end the warm-up operation is acquired and the stack temperature Tfc is equal to or higher than the first threshold temperature Tth1, the warm-up operation is ended. Therefore, quietness can be ensured according to the user's request.

B. Other embodiments:
(B1) In the above-described embodiment, the control unit 20 selects the normal warm-up operation mode or the low-speed warm-up operation mode using the instruction input unit 23, and obtains a warm-up end request. Alternatively, the control unit 20 may select the warm-up operation mode and request the end of the warm-up operation according to the time during which the fuel cell system 100 is being driven. For example, if it is late at night or early in the morning, the low-speed warm-up operation mode may be selected or an end request may be made in order to reduce operating noise.

(B2) In the above embodiment, when the normal warm-up operation mode is selected, the control unit 20 controls the stack temperature Tfc to rise to the first threshold temperature Tth1 and the stack temperature Tfc to rise from the first threshold temperature Tth1. Control is performed so that power generation is performed at the first voltage V1 and the first supply amount Q1 until the temperature rises to the second threshold temperature Tth2. Instead of this, the control unit 20 operates at a third voltage different from the first voltage and a third supply amount different from the first supply amount Q1 until the stack temperature Tfc rises from the first threshold temperature Tth1 to the second threshold temperature Tth2. It may be controlled to generate power. The third voltage is less than the second voltage V2, and the third supply amount is greater than the second supply amount Q2.

The present invention is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments corresponding to the technical features in each form described in the outline of the invention are In addition, it is possible to perform replacement and combination as appropriate. Moreover, if the technical feature is not described as essential in this specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10... Fuel cell stack 11... Fuel cell 20... Control part 22... ECU 23... Instruction input part 30... Cathode gas supply part 31... Cathode gas pipe 32... Air flow meter 33... Compressor 34 First on-off valve 36 Diverter valve 41 Cathode gas discharge pipe 42 First regulator 50 Anode gas supply unit 51 Anode gas pipe 52 Anode gas tank 53 Second on-off valve 54 Second regulator 55 Injector 61 Anode gas discharge pipe 62 Gas-liquid separator 63 Exhaust drain valve 64 Circulation pipe 65 Anode gas pump 66 Circulation passage 70 Cooling medium circulation Part, 71...Refrigerant supply pipe, 72...Refrigerant discharge pipe, 73...Radiator, 74...Refrigerant pump, 75...Three-way valve, 76...Bypass pipe, 77...Temperature measurement unit, 80...DC/DC converter, 81...PCU, 82...Load, 83...Voltage detector, 84...Ammeter, 100...Fuel cell system

Claims (1)

A fuel cell system for warm-up operation having a normal warm-up operation mode and a low-speed warm-up operation mode,
a fuel cell stack;
a compressor that supplies cathode gas to the fuel cell stack;
a temperature measuring unit that acquires the stack temperature of the fuel cell stack;
In the warm-up operation, the output voltage of the fuel cell stack is controlled to a predetermined voltage and the cathode gas supply amount of the compressor is increased until the stack temperature rises to a predetermined first threshold temperature. A control unit that controls a predetermined supply amount,
The control unit
When the normal warm-up operation mode of the warm-up operation is selected, the fuel cell stack is kept warm until the stack temperature rises from the first threshold temperature to a second threshold temperature higher than the first threshold temperature. controlling the output voltage of the compressor to a predetermined first voltage, and controlling the cathode gas supply amount of the compressor to a predetermined first supply amount,
When the low-speed warm-up operation mode is selected from the warm-up operations, the output voltage of the fuel cell stack is increased to the second threshold temperature until the stack temperature rises from the first threshold temperature to the second threshold temperature. Control to a second voltage higher than one voltage, and control the cathode gas supply amount of the compressor to a second supply amount less than the first supply amount,
The fuel cell system obtains a request to end the warm-up operation and ends the warm-up operation when the stack temperature is equal to or higher than the first threshold temperature.

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