JP6935757B2 - Fuel cell system - Google Patents

Description

The techniques disclosed herein relate to fuel cell systems.

Patent Document 1 discloses a fuel cell system. The fuel cell system includes a fuel cell stack, a compressor, an air supply flow path, a pressure regulating valve, a bypass flow path, a bypass valve, a pressure sensor, and a controller. The compressor sends air (oxygen) to the fuel cell stack. The air supply flow path guides the air discharged by the compressor to the fuel cell stack. The pressure regulating valve is provided in a discharge flow path for discharging residual air from the fuel cell stack. The bypass flow path branches from the middle of the air supply flow path, and guides the air discharged by the compressor to the discharge flow path without passing through the fuel cell stack. The bypass valve is provided in the bypass flow path and opens when the pressure on the upstream side exceeds the set pressure. The pressure sensor is provided in the air supply flow path. The controller controls one of the pressure regulating valve and the compressor so that the measured value of the pressure sensor matches the target air pressure.

JP-A-2017-126540

The technology disclosed herein provides a fuel cell system with the ability to detect anomalies in pressure sensors using bypass valves.

The fuel cell system disclosed herein includes a fuel cell stack, a compressor, an air supply flow path, a discharge flow path, a pressure sensor, a bypass flow path, a bypass valve, and a controller. The compressor sends air to the fuel cell stack. The air supply flow path guides the air discharged by the compressor to the fuel cell stack. The pressure sensor measures the pressure in the air supply flow path. The discharge channel discharges residual air from the fuel cell stack. The bypass flow path branches from the middle of the air supply flow path, and guides the air discharged by the compressor to the discharge flow path without passing through the fuel cell stack. The bypass valve is provided in the bypass flow path and is configured to open when the pressure on the upstream side exceeds the set pressure. The controller controls the compressor. The controller drives the compressor until the bypass valve opens to check the pressure sensor. Then, the controller outputs a signal for notifying an abnormality when the pressure difference between the measured value of the pressure sensor and the set pressure when the bypass valve is opened is larger than a predetermined pressure difference threshold value. For the pressure difference, the absolute value of the pressure difference between the measured value of the pressure sensor and the set pressure is used.

When the bypass valve opens, the pressure in the air supply flow path is equal to the set pressure. Therefore, when the bypass valve is opened, the pressure difference between the measured value of the pressure sensor and the set pressure is equal to the pressure difference between the actual pressure of the air supply flow path and the measured value. In other words, the pressure difference between the measured value of the pressure sensor and the set pressure is equal to the measurement error of the pressure sensor. When the pressure difference between the measured value of the pressure sensor and the set pressure when the bypass valve is opened, that is, the measurement error is larger than a predetermined pressure difference threshold value, the controller outputs a signal notifying the abnormality of the pressure sensor. In this fuel cell system, the bypass valve can be used for anomaly detection of the pressure sensor.

When the pressure difference between the measured value of the pressure sensor and the set pressure is smaller than the pressure difference threshold value, it is also preferable that the controller corrects the measured value of the pressure sensor and uses it. Specifically, when the pressure difference is smaller than the pressure difference threshold value, the controller corrects the measured value of the pressure sensor based on the pressure difference. The controller controls the compressor so that the corrected measurements match the target air pressure of the air to be supplied to the fuel cell stack. This fuel cell system can supply air of appropriate pressure to the fuel cell stack by correcting the measurement value of the pressure sensor.

Details of the techniques disclosed herein and further improvements will be described in the "Modes for Carrying Out the Invention" below.

It is a block diagram of the fuel cell system of an Example. It is a schematic structural drawing which shows an example of a bypass valve. It is a flowchart of the pressure sensor check process executed by the controller of the system of an Example.

The fuel cell system 2 of the embodiment will be described with reference to the drawings. FIG. 1 shows a block diagram of the fuel cell system 2. The fuel cell system 2 is a power generation system that generates electricity by an electrochemical reaction between hydrogen and oxygen in the fuel cell stack 30. The broken line in FIG. 1 represents a signal line.

The fuel cell system 2 is mounted on an automobile having a traveling motor. The automobile runs by driving a motor with the electric power generated by the fuel cell system 2.

The fuel cell stack 30 of the embodiment is formed by connecting a large number of power generation units called cells in series. The fuel cell stack 30 generates electricity when hydrogen is supplied to the fuel electrode (anode) and oxygen (air) is supplied to the air electrode (cathode).

Hydrogen is sent from the hydrogen tank 31 to the fuel electrode of the fuel cell stack 30 through the hydrogen supply flow path 32. The hydrogen supply flow path 32 is provided with a sealing valve 33, an injector 34, and a pressure sensor 35. The sealing valve 33 is a valve that opens and closes the mouth of the hydrogen tank 31. The sealing valve 33 is closed while the fuel cell system 2 is stopped. The injector 34 is a valve that adjusts the supply amount of hydrogen gas (fuel gas) to be supplied to the fuel cell stack 30. The pressure sensor 35 is provided on the downstream side of the injector 34 in the hydrogen supply flow path 32. The pressure measured by the pressure sensor 35 is the pressure on the downstream side of the injector 34, that is, the pressure of hydrogen supplied to the fuel electrode of the fuel cell stack 30.

The residual hydrogen gas remaining in the reaction in the fuel cell stack 30 is discharged from the fuel cell stack 30 through the hydrogen discharge flow path 36. The hydrogen discharge flow path 36 joins the discharge flow path 10 described later. The hydrogen discharge flow path 36 is provided with a discharge valve 11.

Oxygen contained in air is used for the reaction with hydrogen gas. The air taken in from the air intake port 5 is compressed by the compressor 4 and supplied to the air electrode of the fuel cell stack 30 through the air supply flow path 6. The residual air remaining after the reaction with hydrogen is discharged to the atmosphere through the discharge channel 10. A pressure regulating valve 9 is provided in the middle of the discharge flow path 10. A muffler 12 is connected downstream of the discharge flow path 10. The air supply flow path 6 is provided with a pressure sensor 13 and a sealing valve 15.

A bypass flow path 8 is connected in the middle of the air supply flow path 6. The bypass flow path 8 branches from the middle of the air supply flow path 6 and is connected to the discharge flow path 10. The bypass flow path 8 guides the air compressed by the compressor 4 to the discharge flow path 10 without passing through the fuel cell stack 30. A bypass valve 20 is provided in the middle of the bypass flow path 8. Further, the bypass valve 20 is provided with a valve sensor 7 that detects an open state and a closed state of the valve.

The compressor 4, the sealing valve 15, the sealing valve 33, the injector 34, the pressure regulating valve 9, the discharge valve 11, and the bypass valve 20 are controlled by the controller 3. The controller 3 determines the pressure of hydrogen gas (target hydrogen pressure) from the target output of the fuel cell stack 30. When the main switch of the fuel cell system 2 is turned on, the controller 3 opens the sealing valve 33 and starts supplying hydrogen gas to the fuel cell stack 30. The controller 3 controls the injector 34 so that the pressure of the hydrogen gas supplied to the fuel cell stack 30 matches the determined target hydrogen pressure. The controller 3 feeds back the measured value of the pressure sensor 35 provided downstream of the injector 34, and controls the injector 34 so that the pressure of the hydrogen gas supplied to the fuel cell stack 30 matches the target hydrogen pressure. ..

Further, the controller 3 opens the sealing valve 15 so that air can be supplied to the fuel cell stack 30. The controller 3 determines the pressure (target air pressure) of the air supplied to the fuel cell stack 30 so that the pressures of the hydrogen gas and the air inside the fuel cell stack 30 are equal to each other. This is because if there is a difference between the pressure of the hydrogen gas and the pressure of the air, the deterioration of the fuel cell stack 30 will progress. The controller 3 controls at least one of the compressor 4 and the pressure regulating valve 9 so that the air pressure supplied to the fuel cell stack 30 (that is, the pressure of the air supply flow path 6) matches the target air pressure. The controller 3 feeds back the measured value of the pressure sensor 13 provided in the air supply flow path 6, and the pressure of the air supplied to the fuel cell stack 30 (that is, the pressure of the air supply flow path 6) is the target air pressure. The compressor 4 is controlled so as to match. The controller 3 may control the pressure regulating valve 9 (or only the pressure regulating valve 9) together with the compressor 4 so that the pressure in the air supply flow path 6 matches the target air pressure.

The air remaining in the reaction is released into the atmosphere through the discharge channel 10 and the muffler 12. The controller 3 controls the discharge valve 11, causes the hydrogen gas remaining in the reaction to flow into the discharge flow path 10 at an appropriate ratio, mixes with the residual air, and discharges the hydrogen gas through the muffler 12.

The bypass flow path 8 provided with the bypass valve 20 has two roles. One is to stop the fuel cell stack 30 and then send high-pressure air to the muffler 12 without passing through the fuel cell stack 30 to discharge the water remaining in the muffler 12. The other is to serve as a relief valve that lowers the internal pressure when the pressure in the air supply flow path 6 becomes excessively high.

Further, in the fuel cell system 2 of this embodiment, the bypass valve 20 is also used for checking the pressure sensor 13. The upstream side of the bypass valve 20 is connected to the air supply flow path 6, and the pressure on the upstream side of the bypass valve 20 is equal to the pressure of the air supply flow path 6. In the fuel cell system 2, a predetermined pressure value is set for the set pressure of the bypass valve 20, and whether or not the pressure sensor 13 is operating properly based on the measured value and the set pressure of the pressure sensor 13 when the bypass valve is opened. Check if.

FIG. 2 shows a schematic structure of an example of the bypass valve 20. The bypass valve 20 opens the valve 21 when the pressure (upstream pressure) on the upstream side 28 exceeds the set pressure. A motor 22 is attached to the rotating shaft of the valve 21. A spring 23 is attached to the valve 21. The spring 23 urges the valve 21 toward the stopper 24. The state in which the valve 21 is pressed against the stopper 24 is the state in which the valve 21 is closed. The motor 22 applies torque in the valve opening direction to the valve 21. The torque obtained by subtracting the torque (motor torque) applied to the valve 21 by the motor 22 from the torque (spring torque) applied to the valve 21 by the spring 23 corresponds to the holding torque for holding the valve 21 in the closed state. When the upstream pressure exceeds the holding torque, the valve 21 opens. That is, the holding torque corresponds to the set pressure of the bypass valve 20. By adjusting the motor torque, the set pressure of the bypass valve 20 can be changed. That is, the bypass valve 20 is a valve that opens when the pressure on the upstream side 28 exceeds the set pressure, and the set pressure can be changed.

The bypass valve 20 is configured such that when the upstream pressure exceeds the set pressure, the opening degree of the valve 21 increases as the upstream pressure increases. The bypass valve 20 is accompanied by a valve sensor 7 that detects whether the valve 21 is in the closed state or the open state, and the detection result of the valve sensor 7 is sent to the controller 3.

The controller 3 uses the bypass valve 20 to check the state of the pressure sensor 13. Next, the pressure sensor check process executed by the controller 3 will be described. 3 and 4 show a flowchart of the pressure sensor check process. The processes of FIGS. 3 and 4 are performed, for example, when the fuel cell system 2 is started or stopped. Later, the pressure sensor check process that can be executed during the power generation of the fuel cell stack 30 will also be mentioned.

First, the controller 3 determines an appropriate set pressure (step S3). The set pressure may be, for example, a target air pressure often adopted during power generation of the fuel cell stack 30. Next, the controller 3 drives the motor 22 so that the determined set pressure is realized by the bypass valve 20 (step S4). Then, the controller 3 drives the compressor 4 until the bypass valve 20 opens (steps S5, S6: NO, S5). The control parameter of the compressor 4 may be the rotation speed, the power consumption, or the air discharge amount. Further, as described above, the controller 3 can detect whether or not the bypass valve 20 has been opened based on the information from the valve sensor 7. At this time, the sealing valve 15 is closed.

When the bypass valve 20 is opened (step S6: YES), the controller 3 compares the pressure difference between the measured value of the pressure sensor 13 and the set pressure of the bypass valve 20 with a predetermined pressure difference threshold value (step S7). The pressure difference here means an absolute value of the pressure difference between the measured value of the pressure sensor 13 and the set pressure. Hereinafter, the pressure difference between the measured value of the pressure sensor 13 and the set pressure is referred to as a pressure difference dPs, and the predetermined pressure difference threshold is referred to as a pressure difference threshold dPt. The pressure difference dPs is given as an absolute value of the pressure difference between the measured value of the pressure sensor 13 and the set pressure. The pressure difference threshold dPt is set to, for example, 20 [kPa].

The fact that the bypass valve 20 is opened means that the actual pressure of the air supply flow path 6 at that time is equal to the set pressure. The fact that the measured value of the pressure sensor 13 at that time deviates from the set pressure means that the measured value of the pressure sensor 13 is not accurate. The pressure difference dPs corresponds to the difference (error) between the actual pressure of the air supply flow path 6 and the measured value of the pressure sensor 13. When the pressure difference dPs is larger than the pressure difference threshold dPt, that is, when the error of the measured value is larger than the pressure difference threshold dPt, the controller 3 determines that the measured value of the pressure sensor 13 cannot be used at all, and causes an abnormality. The notification signal is output (step S7: YES, step S8). The signal notifying the abnormality is sent to, for example, the display device 14 connected to the controller 3. The display device 14 that has received the signal displays a message notifying that an abnormality has occurred in the pressure sensor 13.

On the other hand, when the pressure difference dPs is smaller than the pressure difference threshold dPt, the controller 3 stores the pressure difference dPs as a correction offset (step S7: NO, S9). When sending air to the fuel cell stack 30, the controller 3 uses a value obtained by adding the correction offset to the measured value of the pressure sensor 13 as the correction value of the pressure sensor 13. The pressure difference dPs used as the correction offset is "set pressure-measured value", and in this case, positive and negative signs are included in the pressure difference dPs. That is, when the set pressure is larger than the measured value, the offset becomes a positive value, and when the set pressure is smaller than the measured value, the offset becomes a negative value.

When the fuel cell stack 30 generates electricity, the controller 3 controls the compressor 4 so that the correction value (measured value + offset dPs) of the measured value of the pressure sensor 13 matches the target air pressure. By adopting the correction offset, the pressure of the air sent to the fuel cell stack 30 can be accurately controlled. The fuel cell system 2 can use the bypass valve 20 to check whether or not the measured value of the pressure sensor 13 is appropriate.

After step S9 in FIG. 3, it is also preferable to add a process for checking whether or not the correction offset is appropriate. After setting the offset in step S9, the controller 3 sets the bypass valve 20 in the fully open state. Alternatively, the controller 3 opens the sealing valve 15 and the pressure regulating valve 9 fully. That is, the pressure in the air supply flow path 6 is made equal to the atmospheric pressure. Then, the controller 3 checks whether or not the value obtained by adding the correction offset to the measured value of the pressure sensor 13 is equal to the atmospheric pressure. If the measured value after correction is equal to atmospheric pressure, it can be confirmed that the correction offset is appropriate.

A method of checking the pressure sensor 13 during the operation of the fuel cell stack 30 will be described. As described above, the controller 3 determines the pressure of the air supplied to the fuel cell stack 30 (target air pressure) so that the pressures of the hydrogen gas and the air inside the fuel cell stack 30 are equal to each other. Then, the controller 3 uses the measured value (measured value after correction) of the pressure sensor 13 to drive the compressor 4 so that the pressure in the air supply flow path 6 matches the target air pressure. At this time, the set pressure of the bypass valve 20 is set to a value obtained by adding a margin to the target air pressure. The motor 22 is controlled so that the pressure on the upstream side of the controller 3 and the bypass valve 20 opens when the set pressure is reached.

When the bypass valve 20 opens during the operation of the fuel cell stack 30, the controller 3 compares the measured value of the pressure sensor 13 at that time with the set pressure (that is, the target air pressure + margin). When the pressure difference (absolute value) between the measured value and the set pressure is larger than the pressure difference threshold value, the controller 3 outputs a signal indicating that an abnormality has occurred in the pressure sensor 13. The signal is sent to the display device 14. Upon receiving the signal, the display device 4 displays a message indicating that an abnormality has occurred in the pressure sensor 13. Further, the controller 3 immediately stops the compressor 4 and closes the sealing valves 15 and 33. That is, the power generation in the fuel cell stack 30 is stopped.

The points to be noted regarding the technique described in the examples will be described. The structure shown in FIG. 2 is an example of the bypass valve 20. The structure of the bypass valve 20 is not limited to the structure shown in FIG. The bypass valve 20 may have a structure that can be opened when a pressure exceeding the set value is applied and the set value can be changed.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described herein or in the drawings exhibit their technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in the present specification or drawings can achieve a plurality of purposes at the same time, and achieving one of the purposes itself has technical usefulness.

2: Fuel cell system 3: Controller 4: Compressor 5: Air intake port 6: Air supply flow path 7: Opening sensor 8: Bypass flow path 9: Pressure regulating valve 10: Discharge flow path 11: Discharge valve 12: Muffler 13, 35: Pressure sensor 14: Display 15, 33: Sealing valve 20: Bypass valve 21: Valve 22: Motor 23: Spring 24: Stopper 28: Upstream 30: Fuel cell stack 31: Hydrogen tank 32: Hydrogen supply flow path 34 : Injector 36: Hydrogen discharge flow path

Claims (1)

With the fuel cell stack,
A compressor that sends air to the fuel cell stack,
An air supply flow path that guides the air discharged by the compressor to the fuel cell stack, and
A discharge channel for discharging residual air from the fuel cell stack, and
A pressure sensor that measures the pressure in the air supply flow path and
A bypass flow path that branches from the middle of the air supply flow path and guides the air discharged by the compressor to the discharge flow path without passing through the fuel cell stack.
A bypass valve provided in the bypass flow path and opened when the pressure on the upstream side exceeds a predetermined set pressure.
The controller that controls the compressor and
Is equipped with
The controller drives the compressor until the bypass valve opens.
When the pressure difference between the set pressure when the bypass valve is opened and the measured value of the pressure sensor is larger than a predetermined pressure difference threshold, a signal notifying the abnormality of the pressure sensor is output.
When the pressure difference is smaller than the pressure difference threshold value, the measured value of the pressure sensor is corrected based on the pressure difference.
A fuel cell system that controls the compressor so that the corrected measurements match the target air pressure of the air to be supplied to the fuel cell stack.

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