Fuel cell system

Abstract

This technology provides a way to prevent damage to the muffler. [Solution] The fuel cell system comprises a fuel cell, an air supply pipe for supplying oxidizing gas to the fuel cell, an exhaust pipe for discharging off-gas discharged from the fuel cell to the outside, a muffler provided in the exhaust pipe, and a control device that performs muffler protection control when the estimated value of the pressure inside the muffler exceeds a predetermined threshold.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fuel cell system.

Background Art

[0002] Patent Document 1 discloses a fuel cell system. The fuel cell system of Patent Document 1 includes a fuel cell that receives supply of reaction gas, generates power, and discharges reaction off-gas, a gas passage through which the reaction gas or the reaction off-gas flows, a valve device installed on the gas passage, and a control device that controls the opening degree of the valve device. When starting up the fuel cell system, the control device acquires the downstream pressure of the valve device, and when the downstream pressure is below a predetermined pressurization completion pressure, duty-controls the valve device at a predetermined duty ratio.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a fuel cell system, in order to suppress the noise generated due to the off-gas discharged from the fuel cell, a muffler may be provided in the exhaust pipe. In this configuration, when the exhaust pipe is temporarily blocked or semi-blocked due to freezing or the like, when air is supplied to the fuel cell, there is a risk that the muffler may be damaged due to an increase in the pressure inside the muffler. Therefore, this specification provides a technology that can prevent the muffler from being damaged.

Means for Solving the Problems

[0005] In a first aspect of this technology, the fuel cell system includes a fuel cell, an air supply pipe for supplying an oxidizing gas to the fuel cell, an exhaust pipe for discharging off-gases discharged from the fuel cell to the outside, a muffler provided in the exhaust pipe, and a control device that performs muffler protection control when the estimated value of the pressure inside the muffler exceeds a predetermined threshold.

[0006] This configuration prevents excessive pressure buildup in the muffler by executing muffler protection control when the estimated pressure inside the muffler exceeds a threshold. This prevents damage to the muffler.

[0007] In a second embodiment, the fuel cell system in the first embodiment may include a compressor provided in the air intake pipe for pressurizing the oxidizing gas supplied to the fuel cell, and a pressure sensor for detecting the pressure of the oxidizing gas pressurized by the compressor. The control device may calculate an estimated value of the pressure in the muffler based on the pressure detected by the pressure sensor.

[0008] In a third embodiment, in the second embodiment, the control device may perform the muffler protection control by reducing the rotational speed of the compressor. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing the fuel cell system of the embodiment. [Figure 2] Flowchart (1) of the process performed by the control device of the embodiment. [Figure 3] Flowchart of the process performed by the control device of the embodiment (2). [Modes for carrying out the invention]

[0010] The fuel cell system 2 of the embodiment will be described with reference to the drawings. As shown in Figure 1, the fuel cell system 2 of the embodiment comprises a control device 100, a fuel cell 4, and a first air supply pipe 10, a second air supply pipe 20, a first exhaust pipe 30, and a second exhaust pipe 40 connected to the fuel cell 4. The fuel cell system 2 also comprises a drain pipe 36 and a circulation pipe 50.

[0011] The fuel cell system 2 is installed, for example, in a fuel cell vehicle and supplies power to the vehicle's motor. The fuel cell system 2 may also be used in applications other than fuel cell vehicles. For example, the fuel cell system 2 may be used in a stationary power supply device.

[0012] The control device 100 of the fuel cell system 2 includes, for example, a CPU, ROM, and RAM, and performs control and processing related to the fuel cell system 2 based on a predetermined program. The control and processing performed by the control device 100 will be described later.

[0013] The fuel cell 4 is a device that generates electricity through a chemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidizing gas. The fuel cell 4 is equipped with a stack 4a consisting of multiple single cells. The fuel cell 4 is equipped with one or more stacks 4a. Since the configuration of the fuel cell 4 is already known, a detailed explanation will be omitted.

[0014] The first air supply pipe 10 has its upstream end connected to a fuel gas (for example, a gas containing hydrogen) tank 12, and its downstream end connected to a fuel cell 4. The first air supply pipe 10 supplies the fuel gas stored in the tank 12 to the fuel cell 4. The tank 12 stores the fuel gas for supply to the fuel cell 4 under high pressure.

[0015] The first air supply pipe 10 is equipped with, in order from the upstream side, a tank valve 13, a pressure regulating valve 14, and an inlet valve 18. When the tank valve 13, pressure regulating valve 14, and inlet valve 18 are open, fuel gas is supplied from the tank 12 to the fuel cell 4.

[0016] The pressure regulating valve 14 regulates (reduces) the pressure of the fuel gas in the first air supply pipe 10 so that the pressure of the fuel gas downstream of the pressure regulating valve 14 is lower than the pressure of the fuel gas upstream of the pressure regulating valve 14.

[0017] The second air supply pipe 20 has its upstream end open to the outside of the fuel cell system 2 and its downstream end connected to the fuel cell 4. The second air supply pipe 20 supplies an oxidizing gas (for example, air containing oxygen) supplied from the outside to the fuel cell 4. The second air supply pipe 20 is equipped with, in order from the upstream side, a filter 26, a flow sensor 23, a compressor 22, and a pressure sensor 24.

[0018] The filter 26 removes foreign matter (e.g., dust) contained in the oxidizing gas supplied to the fuel cell 4 through the second air supply pipe 20. The flow sensor 23 detects the flow rate of the oxidizing gas flowing through the second air supply pipe 20. That is, the flow sensor 23 detects the flow rate of the oxidizing gas supplied to the fuel cell 4 through the second air supply pipe 20. The compressor 22 pressurizes the oxidizing gas and pumps it downstream of the second air supply pipe 20. That is, the compressor 22 pressurizes the oxidizing gas supplied to the fuel cell 4. As the compressor 22 operates, the pressurized oxidizing gas is supplied to the fuel cell 4 through the second air supply pipe 20. The pressure sensor 24 detects the pressure of the oxidizing gas in the second air supply pipe 20. That is, the pressure sensor 24 detects the pressure of the oxidizing gas supplied to the fuel cell 4 through the second air supply pipe 20.

[0019] The first exhaust pipe 30 has its upstream end connected to the fuel cell 4 and its downstream end connected to the gas-liquid separator 34. The first exhaust pipe 30 discharges the off-gas of the fuel gas emitted from the fuel cell 4 to the gas-liquid separator 34. The off-gas of the fuel gas contains gaseous hydrogen and liquid water. The first exhaust pipe 30 is provided with an outlet valve 32, and when the outlet valve 32 is open, the off-gas of the fuel gas is discharged from the fuel cell 4 to the gas-liquid separator 34. The gas-liquid separator 34 separates the gas (hydrogen) and liquid (water) contained in the off-gas of the fuel gas.

[0020] The drain pipe 36 has its upstream end connected to the gas-liquid separator 34 and its downstream end open to the outside of the fuel cell system 2. The drain pipe 36 discharges the liquid (water) separated in the gas-liquid separator 34 to the outside of the fuel cell system 2. An on-off valve 38 is provided in the drain pipe 36. When the on-off valve 38 is in the open state, the liquid (water) is discharged from the gas-liquid separator 34 to the outside of the fuel cell system 2. Note that the downstream end of the drain pipe 36 may be connected to the second exhaust pipe 40.

[0021] The circulation pipe 50 has its upstream end connected to the gas-liquid separator 34 and its downstream end connected to the first air supply pipe 10. The downstream end of the circulation pipe 50 is connected to the first air supply pipe 10 on the downstream side of the inlet valve 18. The circulation pipe 50 supplies the gas (hydrogen) separated in the gas-liquid separator 34 to the first air supply pipe 10. A compressor 52 is provided in the circulation pipe 50. When the compressor 52 operates, the gas (hydrogen) separated in the gas-liquid separator 34 is supplied to the first air supply pipe 10.

[0022] The second exhaust pipe 40 has its upstream end connected to the fuel cell 4 and its downstream end open to the outside of the fuel cell system 2. The second exhaust pipe 40 discharges the off-gas of the oxidation gas discharged from the fuel cell 4 to the outside of the fuel cell system 2. A temperature sensor 43, a pressure regulating valve 42, and a muffler 44 are provided in the second exhaust pipe 40 in order from the upstream side.

[0023] The temperature sensor 43 detects the temperature of the off-gas flowing through the second exhaust pipe 40. That is, the temperature sensor 43 detects the temperature of the off-gas discharged from the fuel cell 4 through the second exhaust pipe 40. The pressure regulating valve 42 regulates (reduces the pressure) the pressure of the off-gas in the second exhaust pipe 40 so that the pressure of the off-gas on the downstream side of the pressure regulating valve 42 is lower than the pressure of the off-gas on the upstream side of the pressure regulating valve 42. The pressure regulating valve 42 regulates the pressure of the off-gas in the second exhaust pipe 40 so that the pressure of the oxidation gas in the fuel cell 4 becomes an appropriate pressure.

[0024] The muffler 44 is a device that suppresses noise generated by off-gas flowing through the second exhaust pipe 40. The configuration of the muffler 44 is not particularly limited. For example, the muffler 44 comprises a casing and sound-absorbing material filled inside the casing. In another example, the muffler 44 may have a meandering flow path through which off-gas passes, thereby suppressing noise generated by the off-gas. The off-gas that has passed through the muffler 44 is discharged to the outside of the fuel cell system 2.

[0025] Next, the control and processing performed by the control device 100 will be explained with reference to Figure 2. The processing shown in Figure 2 is started, for example, when a predetermined execution start instruction is input. As shown in Figure 2, in S2 of this processing, the control device 100 determines whether or not oxidizing gas is being supplied to the fuel cell 4. Specifically, the control device 100 determines whether or not the compressor 22 provided in the second air supply pipe 20 is operating. If the compressor 22 is operating (YES in S2), the process proceeds to S4; otherwise (NO in S2), the processing in Figure 2 ends.

[0026] In S4, following the YES response in S2, the control device 100 calculates an estimated value of the pressure inside the muffler 44 located in the second exhaust pipe 40. For example, the control device 100 calculates an estimated value of the pressure inside the muffler 44 based on the pressure detected by the pressure sensor 24, the pressure loss in the fuel cell 4, the pressure loss in the pressure regulating valve 42, and the pressure loss in the second exhaust pipe 40.

[0027] In this case, the pressure loss in the fuel cell 4 is calculated based, for example, on the flow rate of the oxidizing gas and the temperature of the off-gas of the oxidizing gas. The control device 100 calculates the pressure loss in the fuel cell 4 based, for example, on the flow rate detected by the flow sensor 23 provided in the second air supply pipe 20 and the temperature detected by the temperature sensor 43 provided in the second exhaust pipe 40. In a modified example, the pressure loss in the fuel cell 4 may be calculated based on the rotational speed of the compressor 22 and the temperature detected by the temperature sensor 43. In another modified example, the pressure loss in the fuel cell 4 may be calculated based on the flow rate detected by the flow sensor 23 and the temperature of the cooling water in the fuel cell 4. The temperature of the cooling water in the fuel cell 4 is detected by a separate temperature sensor provided in the fuel cell 4.

[0028] The pressure loss in the pressure regulating valve 42 is calculated based, for example, on the flow rate of the oxidizing gas, the temperature of the off-gas for the oxidizing gas, and the opening degree of the pressure regulating valve 42. The control device 100 calculates the pressure loss in the pressure regulating valve 42 based, for example, on the flow rate detected by the flow sensor 23, the temperature detected by the temperature sensor 43, and the opening degree command value of the pressure regulating valve 42.

[0029] The pressure loss in the second exhaust pipe 40 is calculated, for example, based on the flow rate of the oxidizing gas and the temperature of the off-gas of the oxidizing gas. The control device 100 calculates the pressure loss in the second exhaust pipe 40, for example, based on the flow rate detected by the flow sensor 23 and the temperature detected by the temperature sensor 43.

[0030] As shown in Figure 2, in the subsequent S6, the control device 100 determines whether the estimated pressure inside the muffler 44 calculated in S4 exceeds a predetermined threshold. If the estimated pressure inside the muffler 44 exceeds the predetermined threshold (YES in S6), the process proceeds to S8. In S8, the control device 100 turns on muffler abnormality detection. The predetermined threshold can be set as appropriate. On the other hand, if the estimated pressure inside the muffler 44 does not exceed the predetermined threshold (NO in S6), the process shown in Figure 2 ends.

[0031] In S10, following S8, the control device 100 performs muffler protection control. For example, the control device 100 reduces the rotational speed of the compressor 22 installed in the second intake pipe 20. More specifically regarding muffler protection control, as shown in Figure 3, in S22 the control device 100 determines whether the muffler abnormality detection is ON or OFF. If the control device 100 turned on the muffler abnormality detection in S8 (see Figure 2) above, it determines YES in S22. If the muffler abnormality detection is ON (YES in S22), the process proceeds to S24; if it is not ON (NO in S22), the process proceeds to S26.

[0032] In S24, following a YES response in S22, the control device 100 sets the correction value for the rotational speed of the compressor 22. On the other hand, in S26, following a NO response in S22, the control device 100 sets the correction value for the rotational speed of the compressor 22 to 0 (zero).

[0033] In the subsequent S28, the control device 100 sets the command value for the rotational speed of the compressor 22 based on the correction value for the rotational speed of the compressor 22 set in S24 or S26. At this time, the command value for the rotational speed of the compressor 22 = command value for the rotational speed of the compressor 22 - correction value for the rotational speed of the compressor 22. In other words, the command value for the rotational speed of the compressor 22 is the command value obtained by subtracting the correction value from the original command value. Note that if the correction value is 0 (zero) (see S26), the command value for the rotational speed of the compressor 22 is not reduced. The control device 100 outputs the command value set according to the correction value for the rotational speed of the compressor 22 to the compressor 22.

[0034] As a result, if the muffler abnormality detection is ON (see S8, S22), the rotational speed of the compressor 22 is reduced. When the rotational speed of the compressor 22 is reduced, the pressure of the oxidizing gas supplied to the fuel cell 4 through the second intake pipe 20 is reduced, and consequently, the pressure of the off-gas discharged from the fuel cell 4 is reduced. This reduces the pressure of the off-gas supplied to the muffler 44, thus preventing damage to the muffler 44 due to the pressure of the off-gas.

[0035] (effect) The fuel cell system 2 of the embodiment has been described above. As is clear from the above description, the fuel cell system 2 includes a second intake pipe 20 that supplies oxidizing gas to the fuel cell 4, a second exhaust pipe 40 that discharges off-gas discharged from the fuel cell 4 to the outside, a muffler 44 provided in the second exhaust pipe 40, and a control device 100 that performs muffler protection control when the estimated value of the pressure inside the muffler 44 exceeds a predetermined threshold.

[0036] With this configuration, by executing muffler protection control when the estimated pressure inside the muffler 44 exceeds a threshold, it is possible to suppress an excessive rise in pressure inside the muffler 44. This prevents damage to the muffler 44.

[0037] Furthermore, the fuel cell system 2 includes a compressor 22 that pressurizes the oxidizing gas supplied to the fuel cell 4, and a pressure sensor 24 that detects the pressure of the oxidizing gas pressurized by the compressor 22. The control device 100 calculates an estimated value of the pressure inside the muffler 44 based on the pressure detected by the pressure sensor 24. With this configuration, the pressure inside the muffler 44 can be estimated with high accuracy.

[0038] The control device 100 performs muffler protection control by reducing the rotational speed of the compressor 22. This configuration ensures that the pressure inside the muffler 44 is reduced, preventing damage to the muffler 44.

[0039] Furthermore, the fuel cell system 2 of the embodiment does not require additional sensors or actuators, thus reducing costs and size. Also, if a temporary blockage due to freezing of the muffler 44 is resolved, the muffler protection control returns to normal control, eliminating the need for repairs or other measures.

[0040] (modified version) The control device 100 may control the rotational speed of the compressor 22 by feedback control based on the flow rate detected by the flow sensor 23. In other words, the control device 100 may control the rotational speed of the compressor 22 by feedback control based on the flow rate of the oxidizing gas supplied to the fuel cell 4.

[0041] In other variations, the control device 100 may control the rotational speed of the compressor 22 by feedback control based on the output current of the fuel cell 4.

[0042] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of symbols]

[0043] 2: Fuel cell system, 4: Fuel cell, 4a: Stack, 10: First air supply pipe, 12: Tank, 13: Tank valve, 14: Pressure regulating valve, 18: Inlet valve, 20: Second air supply pipe, 22: Compressor, 23: Flow sensor, 24: Pressure sensor, 25: Temperature sensor, 26: Filter, 30: First exhaust pipe, 32: Outlet valve, 34: Gas-liquid separator, 36: Drain pipe, 38: On / off valve, 40: Second exhaust pipe, 42: Pressure regulating valve, 43: Temperature sensor, 44: Muffler, 50: Circulation pipe, 52: Compressor, 100: Control device

Claims

1. Fuel cells and An air supply pipe for supplying oxidizing gas to the fuel cell, An exhaust pipe for discharging off-gas emitted from the fuel cell to the outside, The muffler provided on the exhaust pipe, A fuel cell system comprising: a control device that performs muffler protection control when the estimated pressure inside the muffler exceeds a predetermined threshold;

2. A compressor is provided in the aforementioned air supply pipe and pressurizes the oxidizing gas supplied to the fuel cell, The system includes a pressure sensor that detects the pressure of the oxidizing gas pressurized by the compressor, The fuel cell system according to claim 1, wherein the control device calculates an estimated value of the pressure inside the muffler based on the pressure detected by the pressure sensor.

3. The fuel cell system according to claim 2, wherein the control device performs muffler protection control by reducing the rotational speed of the compressor.

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