Fuel cell system

Abstract

A fuel cell system is provided with a fuel cell, a gas supply pipe for supplying an oxidizing gas to the fuel cell, an exhaust pipe for discharging exhaust gas discharged from the fuel cell to the outside, a muffler provided in the exhaust pipe, and a control device for performing muffler protection control when an estimated value of pressure in the muffler exceeds a predetermined threshold value.

Description

Technical Field

[0001] The technology disclosed in this specification relates to fuel cell systems. Background Technology

[0002] Japanese Patent Application Publication No. 2006-331884 discloses a fuel cell system. The fuel cell system of Japanese Patent Application Publication No. 2006-331884 includes: a fuel cell that receives a supply of reactant gas to generate electricity and discharges reactant waste gas; a gas passage for the flow of reactant gas or reactant waste gas; a valve device installed on the gas passage; and a control device for controlling the opening degree of the valve device. When the fuel cell system is started, the control device obtains the downstream pressure of the valve device, and when the downstream pressure is below a predetermined pressurization completion pressure, it performs duty cycle control on the valve device at a predetermined duty cycle. Summary of the Invention

[0003] In fuel cell systems, mufflers are sometimes installed in the exhaust pipe to suppress noise generated by exhaust gases emitted from the fuel cell. However, in this configuration, if the exhaust pipe is temporarily blocked or partially blocked due to freezing or other reasons, the pressure inside the muffler increases when air is supplied to the fuel cell, potentially causing damage to the muffler. Therefore, this specification provides a technique to prevent muffler damage.

[0004] In a first embodiment of this technology, the fuel cell system comprises: a fuel cell; a gas supply pipe for supplying oxidizing gas to the fuel cell; an exhaust pipe for discharging exhaust gas from the fuel cell to the outside; a muffler disposed in the exhaust pipe; and a control device for performing muffler protection control when a presumed pressure value in the muffler exceeds a predetermined threshold.

[0005] According to this structure, by implementing muffler protection control when the estimated pressure inside the muffler exceeds a threshold, excessive pressure rise inside the muffler can be suppressed. This prevents muffler damage.

[0006] In the second embodiment, as in the first embodiment described above, the fuel cell system includes: a compressor disposed in the gas supply 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.

[0007] Alternatively, the control device may calculate an estimated pressure value within the muffler based on the pressure detected by the pressure sensor.

[0008] In the third approach, or in the second approach described above, the control device performs the muffler protection control by reducing the speed of the compressor.

[0009] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below in conjunction with the accompanying drawings, wherein the same symbols denote the same elements, and the illustrations are as follows. Attached Figure Description

[0010] Figure 1 This is a diagram schematically illustrating an embodiment of a fuel cell system.

[0011] Figure 2 This is a flowchart (1) of the process performed by the control device in the embodiment.

[0012] Figure 3 This is a flowchart (2) of the process performed by the control device in the embodiment. Detailed Implementation

[0013] The fuel cell system 2 of the embodiment will be described with reference to the accompanying drawings. Figure 1 As shown, the fuel cell system 2 of this embodiment includes a control device 100, a fuel cell 4, 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. Additionally, the fuel cell system 2 includes a drain pipe 36 and a circulation pipe 50.

[0014] The fuel cell system 2 is installed, for example, in a fuel cell vehicle, to supply power to the vehicle's motor. The fuel cell system 2 can also be used in devices other than fuel cell vehicles. For example, the fuel cell system 2 can also be used in stationary power supply systems.

[0015] 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 prescribed program. The control and processing performed by the control device 100 will be described later.

[0016] Fuel cell 4 is a device that generates electricity through the chemical reaction of hydrogen contained in fuel gas and oxygen contained in oxidizing gas. Fuel cell 4 includes a stack 4a composed of multiple individual cells. Fuel cell 4 may have one or more stacks 4a. Furthermore, since the structure of fuel cell 4 is already known, detailed descriptions are omitted.

[0017] The upstream end of the first gas supply pipe 10 is connected to a tank 12 containing fuel gas (e.g., a hydrogen-containing gas), and the downstream end is connected to the fuel cell 4. The first gas supply pipe 10 supplies the fuel gas stored in the tank 12 to the fuel cell 4. The tank 12 stores the fuel gas supplied to the fuel cell 4 under high pressure.

[0018] On the first gas supply pipe 10, a tank valve 13, a pressure regulating valve 14, and an inlet valve 18 are sequentially arranged from the upstream side. If the tank valve 13, the pressure regulating valve 14, and the inlet valve 18 are in the open state, fuel gas is supplied from the tank 12 to the fuel cell 4.

[0019] The pressure regulating valve 14 regulates (reduces) the pressure of the fuel gas in the first gas 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.

[0020] The upstream end of the second air supply pipe 20 is open to the outside of the fuel cell system 2, and its downstream end is connected to the fuel cell 4. The second air supply pipe 20 supplies oxidizing gas (e.g., air containing oxygen) supplied from the outside to the fuel cell 4. On the second air supply pipe 20, a filter 26, a flow sensor 23, a compressor 22, and a pressure sensor 24 are arranged sequentially from the upstream side.

[0021] Filter 26 removes foreign matter (e.g., dust) contained in the oxidizing gas supplied to the fuel cell 4 through the second supply pipe 20. Flow sensor 23 detects the flow rate of the oxidizing gas flowing in the second supply pipe 20. That is, flow sensor 23 detects the flow rate of the oxidizing gas supplied to the fuel cell 4 through the second supply pipe 20. Compressor 22 pressurizes the oxidizing gas and pushes it downstream of the second supply pipe 20. That is, compressor 22 pressurizes the oxidizing gas supplied to the fuel cell 4. Through the operation of compressor 22, the pressurized oxidizing gas is supplied to the fuel cell 4 through the second supply pipe 20. Pressure sensor 24 detects the pressure of the oxidizing gas within the second supply pipe 20. That is, pressure sensor 24 detects the pressure of the oxidizing gas supplied to the fuel cell 4 through the second supply pipe 20.

[0022] The upstream end of the first exhaust pipe 30 is connected to the fuel cell 4, and its downstream end is connected to the gas-liquid separator 34. The first exhaust pipe 30 discharges the exhaust gas from the fuel cell 4 to the gas-liquid separator 34. The exhaust gas contains gaseous hydrogen and liquid water. An outlet valve 32 is provided in the first exhaust pipe 30. When the outlet valve 32 is open, the exhaust gas from the fuel cell 4 is discharged to the gas-liquid separator 34. The gas-liquid separator 34 separates the gas (hydrogen) and liquid (water) contained in the exhaust gas.

[0023] The upstream end of the drain pipe 36 is connected to the gas-liquid separator 34, and its downstream end opens 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, liquid (water) is discharged from the gas-liquid separator 34 to the outside of the fuel cell system 2. In addition, the downstream end of the drain pipe 36 can also be connected to the second exhaust pipe 40.

[0024] The upstream end of the circulation pipe 50 is connected to the gas-liquid separator 34, and its downstream end is connected to the first gas supply pipe 10. The downstream end of the circulation pipe 50 is connected to the first gas supply pipe 10 downstream of the inlet valve 18. The circulation pipe 50 supplies the gas (hydrogen) separated in the gas-liquid separator 34 to the first gas supply pipe 10. A compressor 52 is installed in the circulation pipe 50. When the compressor 52 is activated, the gas (hydrogen) separated in the gas-liquid separator 34 is supplied to the first gas supply pipe 10.

[0025] The upstream end of the second exhaust pipe 40 is connected to the fuel cell 4, and its downstream end opens to the outside of the fuel cell system 2. The second exhaust pipe 40 discharges the exhaust gas of the oxidizing gas discharged from the fuel cell 4 to the outside of the fuel cell system 2. On the second exhaust pipe 40, a temperature sensor 43, a pressure regulating valve 42, and a muffler 44 are arranged sequentially from the upstream side.

[0026] Temperature sensor 43 detects the temperature of the exhaust gas flowing through the second exhaust pipe 40. That is, temperature sensor 43 detects the temperature of the exhaust gas discharged from the fuel cell 4 through the second exhaust pipe 40. Pressure regulating valve 42 regulates (depressurizes) the pressure of the exhaust gas in the second exhaust pipe 40 so that the pressure of the exhaust gas downstream of pressure regulating valve 42 is lower than the pressure of the exhaust gas upstream of pressure regulating valve 42. Pressure regulating valve 42 regulates the pressure of the exhaust gas in the second exhaust pipe 40 so that the pressure of the oxidizing gas in the fuel cell 4 is appropriate.

[0027] The muffler 44 is a device for suppressing the sound generated by the exhaust gas flowing through the second exhaust pipe 40. The structure of the muffler 44 is not particularly limited. For example, the muffler 44 includes a housing and sound-absorbing material filled within the housing. In other examples, the muffler 44 may also be a structure with a meandering flow path through which the exhaust gas passes, thereby suppressing the sound generated by the exhaust gas. The exhaust gas passing through the muffler 44 is discharged to the outside of the fuel cell system 2.

[0028] Next, refer to Figure 2 The control and processing performed by the control device 100 are explained. Figure 2 The process shown begins, for example, when a specified execution start instruction is entered. Figure 2As shown, in process S2, the control device 100 determines whether to supply oxidizing gas to the fuel cell 4. Specifically, the control device 100 determines whether the compressor 22 installed in the second gas supply pipe 20 is operating. If the compressor 22 is operating (yes in S2), the process proceeds to S4; otherwise (no in S2). Figure 2 The processing is now complete.

[0029] In S4, following S2, the control device 100 calculates an estimated pressure value within the muffler 44 located in the second exhaust pipe 40. For example, the control device 100 calculates the estimated pressure value within 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.

[0030] At this time, the pressure loss in fuel cell 4 is calculated, for example, based on the flow rate of the oxidizing gas and the temperature of the exhaust gas. Control device 100 calculates the pressure loss in fuel cell 4, for example, based on the flow rate detected by flow sensor 23 installed in the second supply pipe 20 and the temperature detected by temperature sensor 43 installed in the second exhaust pipe 40. Furthermore, in a modified example, the pressure loss in fuel cell 4 can also be calculated based on the rotational speed of compressor 22 and the temperature detected by temperature sensor 43. In other modified examples, the pressure loss in fuel cell 4 can also be calculated based on the flow rate detected by flow sensor 23 and the temperature of cooling water in fuel cell 4. The temperature of the cooling water in fuel cell 4 is detected by another temperature sensor installed in fuel cell 4.

[0031] The pressure loss in the pressure regulating valve 42 is calculated, for example, based on the flow rate of the oxidizing gas, the temperature of the exhaust gas of 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, for example, based on the flow rate detected by the flow sensor 23, the temperature detected by the temperature sensor 43, and the opening command value of the pressure regulating valve 42.

[0032] 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 exhaust 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.

[0033] like Figure 2As shown, in the next step S6, the control device 100 determines whether the estimated pressure value inside the muffler 44 calculated in S4 exceeds a predetermined threshold. If the estimated pressure value inside the muffler 44 exceeds the predetermined threshold (S6: Yes), the process proceeds to S8. In S8, the control device 100 activates the muffler abnormality determination. Furthermore, the predetermined threshold can be appropriately set. On the other hand, if the estimated pressure value inside the muffler 44 does not exceed the predetermined threshold (S6: No). Figure 2 The processing is now complete.

[0034] In S10 following S8, the control device 100 performs muffler protection control. For example, the control device 100 reduces the speed of the compressor 22 installed in the second air supply pipe 20. More specifically regarding the muffler protection control, such as... Figure 3 As shown, in S22, the control device 100 determines whether the muffler malfunction determination is in the open state. The control device 100 in S8 (refer to...) Figure 2 If the muffler malfunction detection is enabled in step S22, the determination is "yes". If the muffler malfunction detection indicates that it is in the enabled state (S22: yes), the process proceeds to step S24; if it is not in the enabled state (S22: no), the process proceeds to step S26.

[0035] In S24, following S22 where it is "yes", the control device 100 sets a correction value for the speed of the compressor 22. On the other hand, in S26, following S22 where it is "no", the control device 100 sets the correction value for the speed of the compressor 22 to 0 (zero).

[0036] In the following step S28, the control device 100 sets the command value for the compressor 22's speed based on the correction value for the compressor 22's speed set in S24 or S26 above. At this time, the command value for the compressor 22's speed = the command value for the compressor 22's speed - the correction value for the compressor 22's speed. That is, the command value for the compressor 22's speed becomes the command value obtained by subtracting the correction value from the original command value. Furthermore, when the correction value is 0 (zero) (refer to S26), the command value for the compressor 22's speed is not reduced. The control device 100 outputs the command value set according to the correction value for the compressor 22's speed to the compressor 22.

[0037] Therefore, when the muffler is abnormally determined to be in the open state (refer to S8, S22), the speed of the compressor 22 is reduced. When the speed of the compressor 22 decreases, the pressure of the oxidizing gas supplied to the fuel cell 4 through the second gas supply pipe 20 decreases, and consequently, the pressure of the exhaust gas discharged from the fuel cell 4 decreases. As a result, the pressure of the exhaust gas supplied to the muffler 44 decreases, thus preventing the muffler 44 from being damaged due to the pressure of the exhaust gas.

[0038] Effect

[0039] The fuel cell system 2 of the embodiment has been described above. As can be seen from the above description, the fuel cell system 2 includes: a second gas supply pipe 20 that supplies oxidizing gas to the fuel cell 4; a second exhaust pipe 40 that discharges the exhaust gas discharged from the fuel cell 4 to the outside; a muffler 44 disposed in the second exhaust pipe 40; and a control device 100 that performs muffler protection control when the estimated pressure in the muffler 44 exceeds a predetermined threshold.

[0040] According to this structure, by performing muffler protection control when the estimated pressure inside the muffler 44 exceeds a threshold, excessive pressure rise inside the muffler 44 can be suppressed. This prevents damage to the muffler 44.

[0041] Furthermore, the fuel cell system 2 includes a compressor 22 for pressurizing the oxidizing gas supplied to the fuel cell 4 and a pressure sensor 24 for detecting 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 structure, the pressure inside the muffler 44 can be estimated with high accuracy.

[0042] The control device 100 performs muffler protection control by reducing the speed of the compressor 22. This structure reliably reduces the pressure inside the muffler 44, preventing damage to the muffler 44.

[0043] Furthermore, the fuel cell system 2 according to the embodiment does not require additional sensors or actuators, thus enabling cost and size reduction. Additionally, in the event of a temporary blockage caused by freezing or other factors in the muffler 44, the muffler protection control returns to normal control, eliminating the need for repairs or other interventions.

[0044] Variations

[0045] The control device 100 can also control the speed of the compressor 22 by feedback control based on the flow rate detected by the flow sensor 23 when controlling the speed of the compressor 22. That is, the control device 100 can also control the speed of the compressor 22 by feedback control based on the flow rate of the oxidizing gas supplied to the fuel cell 4.

[0046] In other variations, the control device 100 may also control the speed of the compressor 22 by feedback control based on the output current of the fuel cell 4 when controlling the speed of the compressor 22.

[0047] While the specific embodiments of the present invention have been described in detail above, these are merely illustrative examples and not intended to limit the scope of the claims. The technical solutions described in the claims include those with various modifications and variations to the above-described exemplary embodiments. The technical elements described in this specification or drawings, whether used individually or in combination, can all demonstrate technical practicality, and their application is not limited to the combinations described in the claims at the time of application. Furthermore, the technology shown in this specification or drawings may simultaneously achieve multiple technical objectives, and even achieving only one objective is itself technically practical.

Claims

1. A fuel cell system, wherein, The fuel cell system comprises: Fuel cells; A gas supply pipe supplies oxidizing gas to the fuel cell; An exhaust pipe discharges the exhaust gas from the fuel cell to the outside. A muffler is installed in the exhaust pipe; as well as The control device performs muffler protection control when the estimated pressure inside the muffler exceeds a predetermined threshold.

2. The fuel cell system according to claim 1, wherein, It comprises: a compressor disposed in the gas supply pipe for pressurizing the oxidizing gas supplied to the fuel cell; and A pressure sensor detects the pressure of the oxidizing gas after it has been pressurized by the compressor. The control device calculates an estimated pressure value 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 the muffler protection control by reducing the speed of the compressor.

Images