Fuel cell system

Abstract

To determine the filter's lifespan with greater accuracy. [Solution] The fuel cell system 20 includes an air flow meter 31, a pressure sensor 32, a pressure regulating valve 30, and a control unit 34. The control unit 34 calculates the differential pressure ΔPcp between the discharge pressure and suction pressure of the air compressor 22 based on the rotational speed of the air compressor 22 when the air flow rate detected by the air flow meter 31 is the target flow rate, and calculates the pressure loss ΔPac due to the filter 29 based on the differential pressure ΔPcp. Taking the value of the pressure loss ΔPac at a predetermined time as a reference value, the control unit 34 determines whether the value obtained by subtracting the reference value from the value of the pressure loss ΔPac calculated in a later period after the predetermined time exceeds a predetermined threshold.

Description

Technical Field

[0001] The present invention relates to a fuel cell system.

Background Art

[0002] For example, as described in Patent Document 1, a fuel cell system includes a fuel cell stack, an air compressor, and an air cleaner. The air compressor supplies air to the fuel cell stack. The air cleaner has a filter. The filter collects dust contained in the air before being inhaled by the air compressor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in such a fuel cell system, when the filter of the air cleaner becomes clogged, the load on the air compressor increases, so it is necessary to replace the filter with a new one. Therefore, in order to efficiently replace the filter, it is necessary to accurately determine the life of the filter.

Means for Solving the Problems

[0005] A fuel cell system that solves the above problems comprises a fuel cell stack, an air compressor that supplies air to the fuel cell stack, and an air cleaner having a filter that collects dust contained in the air before it is drawn into the air compressor, the fuel cell system comprising: an air flow meter that detects the flow rate of air that has passed through the air cleaner and before it is drawn into the air compressor, a pressure sensor that detects the pressure of the air discharged from the air compressor, a pressure regulating valve that adjusts the pressure in the fuel cell stack, and a control unit that controls the rotation speed of the air compressor and the opening degree of the pressure regulating valve so that the pressure detected by the pressure sensor becomes a target pressure, wherein the control unit calculates the differential pressure between the discharge pressure and the intake pressure of the air compressor based on the rotation speed of the air compressor when the flow rate of air detected by the air flow meter is a target flow rate, calculates the pressure loss due to the filter based on the differential pressure, and, using the value of the pressure loss at a predetermined time as a reference value, determines whether the value obtained by subtracting the reference value from the value of the pressure loss calculated in a later period after the predetermined time exceeds a predetermined threshold.

[0006] According to this, for example, if the value obtained by subtracting a reference value from the pressure loss value due to the filter calculated in a later period after a predetermined time exceeds a predetermined threshold, the determination unit can accurately estimate that the pressure loss due to the filter is increasing. Therefore, the lifespan of the filter can be determined with accuracy.

[0007] In the fuel cell system described above, the control unit may calculate the differential pressure based on the rotational speed of the air compressor when the air pressure detected by the pressure sensor is the target pressure.

[0008] This allows for a more accurate determination of the filter's lifespan. [Effects of the Invention]

[0009] According to this invention, the lifespan of a filter can be determined with high accuracy. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a side view showing a forklift in an embodiment. [Figure 2] Figure 2 is a schematic circuit diagram showing the configuration of a fuel cell system. [Figure 3] Figure 3 is a flowchart illustrating the control of the control unit. [Figure 4] Figure 4 is a calculation map that calculates the differential pressure between the discharge pressure and suction pressure of the air compressor based on the relationship between the air flow rate detected by the air flow meter and the rotational speed of the air compressor. [Modes for carrying out the invention]

[0011] An embodiment of the fuel cell system will be described below with reference to Figures 1 to 4. The fuel cell system of this embodiment is mounted on a forklift, which is an industrial vehicle. <Forklift> As shown in Figure 1, the forklift 10 comprises a body 11, a travel motor 12, a cargo handling motor 13, and a fuel cell system 20. The forklift 10 also comprises drive wheels 14 and a cargo handling device 15. The travel motor 12 drives the drive wheels 14. The cargo handling motor 13 drives the cargo handling device 15. The fuel cell system 20 is housed inside the body 11. The body 11 is equipped with a display 16. Therefore, the forklift 10 is equipped with a display 16.

[0012] <Fuel cell system> As shown in Figure 2, the fuel cell system 20 includes a fuel cell stack 21. The fuel cell stack 21 is composed of multiple battery cells stacked on top of each other. The battery cells are of the solid molecular type. The fuel cell stack 21 generates electricity through an electrochemical reaction between hydrogen as a fuel gas and oxygen from the air as an oxidizing gas. The travel motor 12 and the load handling motor 13 of the forklift 10 are driven by the electricity generated by the fuel cell stack 21. The electricity generated by the fuel cell stack 21 is also used to charge a battery (not shown).

[0013] The fuel cell system 20 comprises an air compressor 22, an air cleaner 23, and an intercooler 24. The air compressor 22 is an electric compressor. The air cleaner 23 is connected to the intake port 22a of the air compressor 22 via a first pipe 25. The discharge port 22b of the air compressor 22 is connected to the inlet port 24a of the intercooler 24 via a second pipe 26. The outlet port 24b of the intercooler 24 is connected to the supply port 21a of the fuel cell stack 21 via a third pipe 27. A fourth pipe 28 is connected to the discharge port 21b of the fuel cell stack 21.

[0014] The air cleaner 23 has a filter 29. The filter 29 collects dust contained in the air before it is drawn into the air compressor 22. The air purified by the air cleaner 23 is then drawn into the air compressor 22 via the first pipe 25. The air compressor 22 compresses the air drawn in from the intake port 22a. The air compressed by the air compressor 22 is discharged into the second pipe 26 via the discharge port 22b. The air discharged into the second pipe 26 is supplied to the intercooler 24 and cooled by the intercooler 24. The air cooled by the intercooler 24 is then supplied to the fuel cell stack 21 via the third pipe 27. In this way, the air compressor 22 supplies air to the fuel cell stack 21. The oxygen contained in the air supplied to the fuel cell stack 21 contributes to the power generation of the fuel cell stack 21. After that, the air passing through the fuel cell stack 21 is discharged into the fourth pipe 28 from the exhaust port 21b as exhaust from the fuel cell stack 21.

[0015] The fuel cell system 20 is equipped with a pressure regulating valve 30. The pressure regulating valve 30 is located in the fourth pipe 28. The pressure regulating valve 30 is configured to adjust the flow path cross-sectional area of ​​the fourth pipe 28. The pressure regulating valve 30 adjusts the flow path cross-sectional area of ​​the fourth pipe 28 to regulate the pressure in the fuel cell stack 21. The pressure in the fuel cell stack 21 decreases as the opening of the pressure regulating valve 30 increases. Conversely, the pressure in the fuel cell stack 21 increases as the opening of the pressure regulating valve 30 decreases. In this way, the pressure regulating valve 30 regulates the pressure in the fuel cell stack 21.

[0016] The fuel cell system 20 is equipped with an air flow meter 31. The air flow meter 31 is installed in the first piping 25. The air flow meter 31 is configured to detect the flow rate of air flowing through the first piping 25. Therefore, the air flow meter 31 detects the flow rate of air that has passed through the air cleaner 23 and before it is drawn into the air compressor 22.

[0017] The fuel cell system 20 includes a pressure sensor 32. The pressure sensor 32 is provided in the second pipe 26. The pressure sensor 32 is configured to be able to detect the pressure in the second pipe 26. The pressure in the second pipe 26 is the pressure P6 of the air discharged from the air compressor 22. Therefore, the pressure sensor 32 detects the pressure P6 of the air discharged from the air compressor 22. The value of the pressure P6 of the air discharged from the air compressor 22 is uniquely determined by the value of the pressure loss ΔPout that occurs when the air flows through the second pipe 26. This pressure loss ΔPout can be controlled by the opening degree of the pressure regulating valve 30. Therefore, the pressure P6 of the air discharged from the air compressor 22 can be appropriately adjusted by the opening degree of the pressure regulating valve 30. In the following description, the "pressure P6 of the air discharged from the air compressor 22" may sometimes be simply referred to as "pressure P6".

[0018] The fuel cell system 20 includes an atmospheric pressure sensor 33. The atmospheric pressure sensor 33 is configured to be able to detect the atmospheric pressure Patm. Therefore, the atmospheric pressure sensor 33 detects the atmospheric pressure Patm.

[0019] The fuel cell system 20 includes a control unit 34. The control unit 34 is a host ECU. The control unit 34 can be realized by, for example, one or more dedicated hardware circuits and / or one or more processors (control circuits) that operate according to a computer program (software). The processor includes a CPU and a memory such as a RAM and a ROM, and the memory stores, for example, program codes or instructions configured to cause the processor to execute various processes. The memory, that is, the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0020] The control unit 34 is electrically connected to the air compressor 22. The control unit 34 is electrically connected to the pressure regulating valve 30. The control unit 34 is electrically connected to the atmospheric pressure sensor 33. And information regarding the atmospheric pressure Patm detected by the atmospheric pressure sensor 33 is transmitted to the control unit 34.

[0021] The control unit 34 is electrically connected to the pressure sensor 32. Information regarding the pressure detected by the pressure sensor 32 is transmitted to the control unit 34. A control program for controlling the rotational speed of the air compressor 22 and the opening degree of the pressure regulating valve 30 is stored in advance in the control unit 34 so that the pressure detected by the pressure sensor 32 becomes the target pressure. Thus, the control unit 34 controls the rotational speed of the air compressor 22 and the opening degree of the pressure regulating valve 30 so that the pressure detected by the pressure sensor 32 becomes the target pressure. Specifically, the rotational speed of the air compressor 22 is the rotational speed of the motor of the air compressor 22.

[0022] The control unit 34 is electrically connected to the air flow meter 31. Information regarding the air flow rate detected by the air flow meter 31 is transmitted to the control unit 34. A differential pressure calculation program for calculating the differential pressure ΔPcp between the discharge pressure and the suction pressure of the air compressor 22 based on the rotational speed of the air compressor 22 when the air flow rate detected by the air flow meter 31 is the target flow rate and the air pressure detected by the pressure sensor 32 is the target pressure is stored in advance in the control unit 34. Thus, the control unit 34 calculates the differential pressure ΔPcp between the discharge pressure and the suction pressure of the air compressor 22 based on the rotational speed of the air compressor 22 when the air flow rate detected by the air flow meter 31 is the target flow rate. Further, the control unit 34 calculates the differential pressure ΔPcp between the discharge pressure and the suction pressure of the air compressor 22 based on the rotational speed of the air compressor 22 when the air pressure detected by the pressure sensor 32 is the target pressure. In the following description, the "differential pressure ΔPcp between the discharge pressure and the suction pressure of the air compressor 22" may sometimes be simply referred to as "differential pressure ΔPcp".

[0023] In addition, the differential pressure ΔPcp may be calculated based on the rotational speed of the air compressor 22 when the temperature of the air compressor 22 is at a predetermined temperature condition, in addition to the air flow rate detected by the air flow meter 31 being the target flow rate and the air pressure detected by the pressure sensor 32 being the target pressure. The temperature of the air compressor 22 is the temperature of the motor of the air compressor 22.

[0024] The control unit 34 has a pressure calculation program pre-stored that calculates the pressure loss ΔPac due to the filter 29 based on the differential pressure ΔPcp. In the following description, "pressure loss ΔPac due to filter 29" may also be simply referred to as "pressure loss ΔPac".

[0025] Here, considering the pressure loss ΔPin that occurs when air flows through the first pipe 25 and the pressure loss ΔPout that occurs when air flows through the second pipe 26, the pressure P6 can be calculated by the following equation (1).

[0026] P6=Patm-ΔPac-ΔPin+ΔPcp-ΔPout…(1) Therefore, the pressure loss ΔPac can be calculated using the following equation (2). ΔPac=Patm-ΔPin+ΔPcp-ΔPout-P6…(2) In this way, the control unit 34 calculates the pressure loss ΔPac due to the filter 29 based on the differential pressure ΔPcp.

[0027] The control unit 34 has a pre-programmed function to store as a reference value the pressure loss ΔPac value calculated by the filter 29 during the initial period when the fuel cell system 20 is first started. The initial period is a predetermined time. The control unit 34 also has a pre-programmed function to determine whether the value obtained by subtracting the reference value from the pressure loss ΔPac value calculated during the later period (after the initial period) exceeds a predetermined threshold. Thus, the control unit 34 functions as a determination unit to determine whether the value obtained by subtracting the reference value from the pressure loss ΔPac value calculated during the later period (after the predetermined time) exceeds a predetermined threshold. Therefore, the control unit 34 includes a determination unit.

[0028] The control unit 34 is electrically connected to the display 16. When the control unit 34 determines that the value obtained by subtracting a reference value from the pressure loss ΔPac due to the filter 29 calculated in the later stages exceeds a predetermined threshold, it displays a notification screen on the display 16 indicating that it is time to replace the filter 29.

[0029] [Effect of the Embodiment] Next, the operation of the embodiment will be described. As shown in Figure 3, in step S11, the control unit 34 first stores the initially calculated pressure loss ΔPac due to the filter 29 as a reference value. Subsequently, in step S12, the control unit 34 calculates the pressure loss ΔPac due to the filter 29.

[0030] Figure 4 is a calculation map for calculating the differential pressure ΔPcp between the discharge pressure and suction pressure of the air compressor 22 from the relationship between the air flow rate detected by the air flow meter 31 and the rotational speed of the air compressor 22. In Figure 4, the dashed line L1 shows the initial rotational speed of the air compressor 22 when the air flow rate detected by the air flow meter 31 is the target flow rate and the air pressure detected by the pressure sensor 32 is the target pressure. The solid line L2 shows the later rotational speed of the air compressor 22 when the air flow rate detected by the air flow meter 31 is the target flow rate and the air pressure detected by the pressure sensor 32 is the target pressure. "Later" refers to a period, for example, several months after the initial stage.

[0031] As shown in Figure 4, in the later stage, the rotational speed of the air compressor 22 when the air flow rate detected by the air flow meter 31 is equal to the target flow rate is higher than in the initial stage. Therefore, the differential pressure ΔPcp calculated based on the rotational speed of the air compressor 22 when the air flow rate detected by the air flow meter 31 is equal to the target flow rate is larger in the later stage than in the initial stage.

[0032] If the air flow rate detected by the air flow meter 31 is the target flow rate and the air pressure detected by the pressure sensor 32 is the target pressure, and the rotational speed of the air compressor 22 in the later stages is higher than in the initial stages, it can be estimated that the intake pressure of the air compressor 22 has decreased. In this case, assuming that the atmospheric pressure Patm is the same in the initial and later stages, the pressure loss ΔPac due to the filter 29 can be estimated.

[0033] The control unit 34 calculates the pressure loss ΔPac due to the filter 29 based on the differential pressure ΔPcp calculated initially, and stores this value as a reference value. Furthermore, the control unit 34 calculates the pressure loss ΔPac due to the filter 29 based on the differential pressure ΔPcp calculated later. Here, the differential pressure ΔPcp used when calculating the pressure loss ΔPac due to the filter 29 is calculated based on the rotational speed of the air compressor 22 when the temperature of the air compressor 22 is under predetermined temperature conditions, both initially and later. This improves the accuracy of calculating the pressure loss ΔPac due to the filter 29.

[0034] As shown in Figure 3, in step S13, the control unit 34 determines whether the value obtained by subtracting the reference value from the pressure loss ΔPac calculated in step S12 exceeds a predetermined threshold. If the control unit 34 determines in step S13 that the value obtained by subtracting the reference value from the pressure loss ΔPac calculated in step S12 exceeds a predetermined threshold, it proceeds to step S14. Then, in step S14, the control unit 34 displays a notification screen on the display 16 indicating that it is time to replace the filter 29. On the other hand, if the control unit 34 determines in step S13 that the value obtained by subtracting the reference value from the pressure loss ΔPac calculated in step S12 does not exceed a predetermined threshold, it proceeds to step S12.

[0035] [Effects of the Embodiment] The above embodiment can be achieved to obtain the following effects. (1) For example, if the control unit 34 determines that the value obtained by subtracting a reference value from the pressure loss ΔPac value due to the filter 29 calculated in the later stage (after the initial stage) exceeds a predetermined threshold, it can accurately estimate that the pressure loss ΔPac due to the filter 29 is increasing. Therefore, the lifespan of the filter 29 can be determined with accuracy.

[0036] (2) The control unit 34 calculates the differential pressure ΔPcp based on the rotational speed of the air compressor 22 when the air pressure detected by the pressure sensor 32 is the target pressure. This allows for a more accurate determination of the lifespan of the filter 29.

[0037] (3) The control unit 34 determines whether the value obtained by subtracting a reference value from the pressure loss ΔPac value calculated after the initial operation exceeds a predetermined threshold. Therefore, since the lifespan of the filter 29 is determined by comparing the same air compressor 22 before and after operation, variations in the characteristic curve indicating the rotational speed of the air compressor 22 due to individual differences in the air compressor 22 do not affect the determination of the lifespan of the filter 29. Thus, the lifespan of the filter 29 can be determined with high accuracy.

[0038] (4) The lifespan of the filter 29 can be determined with accuracy, allowing for efficient replacement of the filter 29. Therefore, there is no need to use an unnecessarily large filter 29 in order to avoid the need to replace the filter 29 for a certain period of time. Consequently, the filter 29 can be made smaller.

[0039] (5) The lifespan of the filter 29 can be determined with accuracy, making it easy to determine when to replace it. Therefore, the user of the forklift 10 does not need to rely on a service technician to determine when to replace the filter 29. Consequently, the replacement of the filter 29 can be done efficiently.

[0040] (6) Since the filter 29 can be replaced efficiently, it is possible to avoid the fuel cell system 20 being operated with a clogged filter 29. As a result, it is possible to avoid problems such as the air compressor 22's compression efficiency deteriorating, which would prevent efficient air supply to the fuel cell stack 21 and thus worsen the power generation efficiency of the fuel cell stack 21.

[0041] [Example of changes] The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0042] ○ In this embodiment, the predetermined time is not limited to the initial period when the fuel cell system 20 is first started. For example, the predetermined time may be when a certain period of time has elapsed since the fuel cell system 20 started up, and then the predetermined conditions are met for the first time. The predetermined conditions are, for example, when the power generation mode of the fuel cell stack 21 is set to a predetermined mode.

[0043] ○ In this embodiment, the control unit 34 may, for example, send a message to the cloud indicating that it is time to replace the filter 29, and notify a service technician who will perform the filter 29 replacement work.

[0044] ○ In this embodiment, the control unit 34 may, for example, notify the user that it is time to replace the filter 29 by lighting up a lamp provided on the forklift 10.

[0045] ○ In this embodiment, the determination unit may be an ECU separate from the control unit 34. ○ In this embodiment, the fuel cell system 20 is mounted on a forklift 10, but it is not limited to this, and may be mounted on, for example, a towing vehicle used for transporting goods, or an order picker used for picking operations. In short, the fuel cell system 20 may be mounted on industrial vehicles other than the forklift 10.

[0046] ○ In this embodiment, the fuel cell system 20 may be installed in a fuel cell vehicle other than an industrial vehicle. ○ In this embodiment, the fuel cell system 20 may be mounted on a stationary power generation device. [Explanation of Symbols]

[0047] 20...Fuel cell system, 21...Fuel cell stack, 22...Air compressor, 23...Air cleaner, 29...Filter, 30...Pressure regulating valve, 31...Air flow meter, 32...Pressure sensor, 34...Control unit functioning as a judgment unit.

Claims

1. Fuel cell stack and An air compressor that supplies air to the fuel cell stack, A fuel cell system comprising: an air cleaner having a filter for collecting dust contained in the air before it is drawn into the air compressor, An air flow meter that detects the flow rate of air that has passed through the air cleaner and is before being drawn into the air compressor, A pressure sensor for detecting the pressure of the air discharged from the air compressor, A pressure regulating valve for adjusting the pressure within the fuel cell stack, The system includes a control unit that controls the rotational speed of the air compressor and the opening degree of the pressure regulating valve so that the pressure detected by the pressure sensor becomes the target pressure, The fuel cell system is characterized in that the control unit calculates the differential pressure between the discharge pressure and suction pressure of the air compressor based on the rotational speed of the air compressor when the air flow rate detected by the air flow meter is a target flow rate, calculates the pressure loss due to the filter based on the differential pressure, and determines whether the value obtained by subtracting the reference value from the pressure loss value calculated in a later period after the predetermined period exceeds a predetermined threshold, using the value of the pressure loss at a predetermined time as a reference value.

2. The fuel cell system according to claim 1, characterized in that the control unit calculates the differential pressure based on the rotational speed of the air compressor when the air pressure detected by the pressure sensor is the target pressure.

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