Fuel cell unit

Abstract

To suppress a sudden change in a flow rate of a cathode gas in a cathode flow path that occurs as an opening degree of a pressure regulating valve becomes smaller.SOLUTION: A fuel cell unit 20 includes a fuel cell stack 21 that generates electricity through a reaction between an anode gas supplied to an anode flow path 60a and a cathode gas supplied to a cathode flow path 30a, a pressure regulating valve 41 that is provided on a downstream side of the fuel cell stack 21 in the cathode flow path 30a and whose opening degree becomes smaller as a valve body approaches a seat surface, and a control unit 80 that controls the opening degree of the pressure regulating valve 41 by moving the valve body, and the control unit 80 moves the valve body such that a speed at which the opening degree of the pressure regulating valve 41 is reduced when the opening degree of the pressure regulating valve 41 is equal to or less than a first opening degree is slower than a speed at which the opening degree of the pressure regulating valve 41 is reduced when the opening degree of the pressure regulating valve 41 is larger than the first opening degree.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] The fuel cell unit described in Patent Document 1 includes a fuel cell stack, a pressure regulating valve, and a control unit. The fuel cell stack generates power through a reaction between an anode gas supplied to an anode flow path and a cathode gas supplied to a cathode flow path. The pressure regulating valve is provided downstream of the fuel cell stack in the cathode flow path. The control unit controls the opening degree of the pressure regulating valve.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In a pressure regulating valve whose opening degree decreases as the valve body approaches the seat surface, the pressure regulating valve has a low opening degree region from a predetermined opening degree where the valve body is relatively close to the seat surface to full closure. When reducing the opening degree of the pressure regulating valve in the low opening degree region, the degree of change in the effective cross-sectional area, which is the cross-sectional area of the portion where gas flows between the valve body and the seat surface among the flow path cross-sectional area of the cathode flow path, increases. Therefore, there is a risk that the flow rate of gas in the cathode flow path passing through the pressure regulating valve may suddenly change. Such behavior is not preferable because it leads to a decrease in output of the fuel cell stack.

Means for Solving the Problem

[0005] A fuel cell unit that solves the above problems comprises a fuel cell stack that generates electricity by a reaction between an anode gas supplied to an anode channel and a cathode gas supplied to a cathode channel, a pressure regulating valve provided downstream of the fuel cell stack in the cathode channel, the valve opening decreases as the valve body approaches the seat surface, and a control unit that controls the opening of the pressure regulating valve by moving the valve body, wherein the control unit moves the valve body at a slower speed when reducing the opening of the pressure regulating valve when the opening of the pressure regulating valve is less than or equal to a first opening than the speed when reducing the opening of the pressure regulating valve when the opening of the pressure regulating valve is greater than the first opening.

[0006] According to the above configuration, when the opening degree of the pressure regulating valve is below the first opening degree, it is possible to suppress the rapid change in the flow rate of cathode gas in the cathode flow path that occurs as the opening degree of the pressure regulating valve decreases.

[0007] In a fuel cell unit, the control unit may move the valve body at a speed faster than the speed at which it reduces the opening of the pressure regulating valve when the opening of the pressure regulating valve is greater than the first opening and less than the second opening, when the opening of the pressure regulating valve is greater than the first opening and less than the second opening.

[0008] According to the above configuration, when reducing the opening of the pressure regulating valve, the speed at which the valve body moves can be gradually slowed down when the opening of the pressure regulating valve is greater than or equal to the second opening, greater than or equal to the first opening but less than or equal to the second opening, and less than or equal to the first opening. Therefore, compared to the case where the speed at which the valve body moves is changed in two stages, when the opening of the pressure regulating valve is greater than the first opening and when it is less than or equal to the first opening, the abrupt change in the flow rate of cathode gas in the cathode flow path that occurs when the opening of the pressure regulating valve decreases can be further suppressed.

[0009] In a fuel cell unit, when the control unit increases the opening of the pressure regulating valve, it may move the valve body at a faster speed than when it decreases the opening of the pressure regulating valve when the opening of the pressure regulating valve is less than or equal to the first opening.

[0010] With the above configuration, when increasing the opening of the pressure regulating valve, which is less likely to cause abrupt changes in the cathode gas flow rate in the cathode channel, the valve body can be moved earlier, thereby improving the responsiveness of the pressure regulating valve opening change.

[0011] In a fuel cell unit, the pressure regulating valve may be a butterfly valve in which the valve body rotates, bringing the valve body closer to the seating surface. In a fuel cell unit, the fuel cell stack generates power while switching between a plurality of target powers, including a first target power and a second target power that is smaller than the first target power, and the control unit may control the opening degree of the pressure regulating valve to be less than or equal to the first opening degree when the target power is the first target power.

[0012] With the above configuration, by adjusting the movement speed of the valve body, abrupt changes in the flow rate of cathode gas in the cathode flow path can be suppressed. Therefore, by adjusting the opening of the pressure regulating valve over a wider range of openings, including the opening range of the pressure regulating valve below the first opening, the target power can be controlled. [Effects of the Invention]

[0013] According to this invention, it is possible to suppress the rapid change in the flow rate of cathode gas in the cathode channel that occurs as the opening degree of the pressure regulating valve decreases. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of a fuel cell unit in an embodiment. [Figure 2] This is a schematic diagram showing a pressure regulating valve. [Figure 3] This is a cross-sectional view showing a pressure regulating valve. [Figure 4] This is a cross-sectional view showing a pressure regulating valve. [Figure 5] It is a flowchart showing the processing procedure of speed control. [Figure 6] It is a graph showing the relationship between time and the opening degree of a pressure regulating valve. MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, embodiments embodying a fuel cell unit will be described with reference to the drawings. As shown in Fig. 1, an industrial vehicle 10 includes a load 11, a power conversion unit 12, a key switch 13, and a fuel cell unit 20. The industrial vehicle 10 is, for example, a forklift or a towing tractor.

[0016] The load 11 is a device driven by electric power. The load 11 is, for example, an electric motor driven by electric power. The industrial vehicle 10 travels by the driving of this electric motor. The power conversion unit 12 converts power input from the fuel cell unit 20 to the power conversion unit 12 and outputs the converted power. The power conversion unit 12 includes a DC / DC converter and an inverter. The power output from the power conversion unit 12 is supplied to the load 11, whereby the load 11 is driven.

[0017] The key switch 13 is operated by a user of the industrial vehicle 10. The key switch 13 is switched between on and off by an operation performed by the user. In the following description, turning off the key switch 13 may be referred to as key-off, and turning on the key switch 13 may be referred to as key-on.

[0018] <Fuel Cell Unit> The fuel cell unit 20 comprises a cathode system 30, an anode system 60, and a diluter 69. The fuel cell unit 20 comprises a fuel cell stack 21 and a control unit 80. The fuel cell stack 21 is, for example, a polymer electrolyte fuel cell. The fuel cell stack 21 includes a plurality of fuel cells 22. The fuel cell 22 comprises an anode electrode to which anode gas is supplied, a cathode electrode to which cathode gas is supplied, and an electrolyte membrane disposed between the anode electrode and the cathode electrode. The fuel cells 22 are sandwiched between separators.

[0019] The cathode system 30 includes a cathode flow path 30a. The cathode flow path 30a includes an internal cathode flow path 23 that flows inside the fuel cell stack 21. Cathode gas flows through the internal cathode flow path 23. The internal cathode flow path 23 is provided, for example, in a separator facing the cathode electrode in the fuel cell stack 21. The internal cathode flow path 23 comprises an inflow port 24 and an outflow port 25. The cathode gas flows into the internal cathode flow path 23 from the inflow port 24, and flows out of the internal cathode flow path 23 from the outflow port 25.

[0020] The anode system 60 includes an anode flow path 60a. The anode flow path 60a includes an internal anode flow path 26 that flows inside the fuel cell stack 21. Anode gas flows through the internal anode flow path 26. The internal anode flow path 26 is provided, for example, in a separator facing the anode electrode in the fuel cell stack 21. The internal anode flow path 26 comprises an inflow port 27 and an outflow port 28. The anode gas flows into the internal anode flow path 26 from the inflow port 27, and flows out of the internal anode flow path 26 from the outflow port 28.

[0021] The fuel cell stack 21 generates electricity through the reaction between the anode gas flowing through the anode internal channel 26 and the cathode gas flowing through the cathode internal channel 23. In other words, the fuel cell stack 21 generates electricity through the reaction between the anode gas supplied to the anode channel 60a and the cathode gas supplied to the cathode channel 30a. The cathode gas is an oxidizing gas. An example of an oxidizing gas is oxygen from the air. The anode gas is a fuel gas. An example of a fuel gas is hydrogen gas.

[0022] The anode system 60 includes a tank 61, an anode gas supply unit 62, a gas-liquid separator 65, a circulation pump 66, and an exhaust drain valve 67. The anode flow path 60a includes a supply path 63 and a circulation path 64.

[0023] Tank 61 stores anode gas. Anode gas is supplied from Tank 61 to the anode gas supply unit 62. The anode gas supply unit 62 is a component for adjusting the amount of anode gas supplied to the fuel cell stack 21. The amount of anode gas supplied to the fuel cell stack 21 can be adjusted by controlling the anode gas supply unit 62. For example, a solenoid valve such as an injector can be used as the anode gas supply unit 62.

[0024] The supply channel 63 connects the anode gas supply unit 62 to the inlet 27 of the anode internal flow path 26. The anode gas injected from the anode gas supply unit 62 is supplied to the fuel cell stack 21 through the supply channel 63.

[0025] The circulation path 64 connects the outlet 28 of the anode internal flow path 26 to the supply path 63. Anode exhaust gas flows through the circulation path 64. The anode exhaust gas contains unreacted anode gas and generated water. The generated water is water produced by the power generation in the fuel cell stack 21. The circulation path 64 is a passage for returning the unreacted anode gas contained in the anode exhaust gas back to the supply path 63.

[0026] The gas-liquid separator 65 is installed in the circulation path 64. The gas-liquid separator 65 separates the anode exhaust gas into anode gas and generated water. The generated water separated from the anode exhaust gas is stored in the gas-liquid separator 65.

[0027] The circulation pump 66 is located in the circulation path 64. The circulation pump 66 supplies the anode gas separated from the anode exhaust gas by the gas-liquid separator 65 to the supply path 63. This causes the anode gas to circulate.

[0028] The exhaust and drain valve 67 is connected to the gas-liquid separator 65. The exhaust and drain valve 67 can be switched between an open state and a closed state. When the exhaust and drain valve 67 is open, the generated water is discharged from the gas-liquid separator 65. The exhaust and drain valve 67 may be switched from the closed state to the open state when the amount of generated water stored in the gas-liquid separator 65 exceeds a threshold. The exhaust and drain valve 67 may be switched from the closed state to the open state at predetermined time intervals.

[0029] The gas-liquid separator 65 is connected to the diluent 69. When the exhaust drain valve 67 is open, the generated water and anode exhaust gas stored in the gas-liquid separator 65 are supplied to the diluent 69. The cathode system 30 includes a cathode gas inlet 31, an electric compressor 32, an intercooler 33, a sealing valve 40, and a pressure regulating valve 41. In other words, the fuel cell unit 20 has a pressure regulating valve 41. The cathode flow path 30a includes a cathode supply path 34 and a cathode discharge path 37.

[0030] The cathode gas inlet 31 is an inlet for drawing cathode gas into the fuel cell unit 20. When oxygen from the air is used as the cathode gas, the cathode gas inlet 31 may be open to the atmosphere. The cathode gas inlet 31 may be connected to a gas cylinder for storing cathode gas.

[0031] The electric compressor 32 is driven by an electric motor. The electric compressor 32 supplies cathode gas to the fuel cell stack 21. More specifically, the electric compressor 32 compresses the cathode gas supplied from the cathode gas inlet 31 and supplies it to the fuel cell stack 21. The cathode gas may be supplied from the cathode gas inlet 31 to the electric compressor 32 through an air cleaner (not shown). The cathode gas supplied from the electric compressor 32 to the fuel cell stack 21 flows through the cathode internal passage 23.

[0032] The intercooler 33 is supplied with cathode gas discharged from the electric compressor 32. The intercooler 33 cools the cathode gas supplied from the electric compressor 32. The cathode gas supplied to the fuel cell stack 21 is the cathode gas that has been cooled by the intercooler 33.

[0033] The cathode supply passage 34 is the portion of the cathode flow path 30a located upstream of the fuel cell stack 21. The cathode supply passage 34 connects the electric compressor 32 to the inlet 24 of the cathode internal flow path 23. The cathode supply passage 34 includes a first supply passage 35 and a second supply passage 36. The first supply passage 35 connects the electric compressor 32 to the intercooler 33. The second supply passage 36 connects the intercooler 33 to the inlet 24 of the cathode internal flow path 23.

[0034] The cathode discharge channel 37 is the portion of the cathode flow path 30a located downstream of the fuel cell stack 21. The cathode discharge channel 37 connects the outlet 25 of the cathode internal flow path 23 to the diluent 69. The cathode discharge channel 37 is the flow path through which the cathode exhaust gas flows. The cathode exhaust gas is the cathode gas discharged from the fuel cell stack 21 and contains generated water. The cathode exhaust gas is discharged from the cathode discharge channel 37 to the diluent 69. The diluent 69 dilutes the anode exhaust gas supplied from the gas-liquid separator 65 with the cathode exhaust gas and discharges it into the atmosphere.

[0035] The sealing valve 40 is provided in the cathode supply passage 34. In this embodiment, the sealing valve 40 is provided in the second supply passage 36. The sealing valve 40 may also be provided in the first supply passage 35. The sealing valve 40 is, for example, a butterfly valve that seals the cathode supply passage 34. The sealing valve 40 can be switched between an open state and a closed state. When the sealing valve 40 is open, cathode gas is supplied to the cathode internal passage 23 via the cathode supply passage 34. When the sealing valve 40 is closed, the cathode supply passage 34 is sealed.

[0036] <Pressure Regulating Valve> The pressure regulating valve 41 is located in the cathode discharge passage 37. Therefore, the pressure regulating valve 41 is located downstream of the fuel cell stack 21 in the cathode flow path 30a. The pressure regulating valve 41 is a butterfly valve. The internal pressure of the fuel cell stack 21 is adjusted by adjusting the opening degree of the pressure regulating valve 41. The smaller the opening degree of the pressure regulating valve 41, the higher the internal pressure of the fuel cell stack 21. When the pressure regulating valve 41 is fully closed, the cathode discharge passage 37 is sealed.

[0037] As shown in Figure 2, the pressure regulating valve 41 comprises a body 42, a sealing member 44, a valve body 48, a rotating shaft 51, a reduction mechanism 52, a motor 54, a drive unit 55, an opening sensor 58, and a stopper 59. The body 42 has a flow path 43 that passes through the body 42. That is, the body 42 is cylindrical. Because the body 42 is installed in the cathode discharge passage 37, the flow path 43 is in communication with the cathode discharge passage 37.

[0038] The sealing member 44 is provided in the flow path 43. The sealing member 44 is made of, for example, rubber. The sealing member 44 is annular in shape. The sealing member 44 has a seating surface 44a. The seating surface 44a is the inner circumferential surface of the sealing member 44. The sealing member 44 includes a tapered portion 45. The tapered portion 45 is the part of the sealing member 44 in which the inner diameter decreases from the first end 46 in the axial direction of the sealing member 44 toward the second end 47. The sealing member 44 is provided along the inner circumferential surface of the body 42.

[0039] The valve body 48 is provided in the flow path 43. The valve body 48 comprises a main body 49 and a connecting portion 50. The main body 49 is disc-shaped. The diameter of the main body 49 is smaller than the maximum inner diameter of the tapered portion 45 and larger than the minimum inner diameter of the tapered portion 45.

[0040] The rotating shaft 51 is provided in the connecting portion 50. The valve body 48 rotates as the rotating shaft 51 rotates. The rotation of the valve body 48 as the rotating shaft 51 rotates adjusts the opening degree of the pressure regulating valve 41. When the pressure regulating valve 41 is fully closed, the valve body 48 is in close contact with the sealing member 44. This seals the flow path 43. The sealing member 44 seals the valve body 48.

[0041] As shown in Figure 3, in the pressure regulating valve 41, the opening degree increases as the valve body 48 moves away from the seat surface 44a. In the pressure regulating valve 41, the opening degree decreases as the valve body 48 moves closer to the seat surface 44a. In the pressure regulating valve 41, the valve body 48 moves closer to the seat surface 44a as it rotates.

[0042] Of the flow path cross-sectional area of ​​the flow path 43, the portion where gas flows between the valve body 48 and the seat surface 44a will hereafter be referred to as the effective cross-sectional area of ​​the pressure regulating valve 41. The effective cross-sectional area decreases as the valve body 48 approaches the seat surface 44a. That is, the smaller the opening degree of the pressure regulating valve 41, the smaller the effective cross-sectional area of ​​the pressure regulating valve 41 becomes.

[0043] As shown in Figure 4, the pressure regulating valve 41 has a region in which the valve body 48 is in contact with the seat surface 44a, but the pressure regulating valve 41 is not fully closed. This region will be referred to as the low-opening region below. After the valve body 48 moves from a position away from the seat surface 44a to a position closer to the seat surface 44a, the valve body 48 comes into contact with the seat surface 44a, and the opening of the pressure regulating valve 41 becomes the opening in the low-opening region.

[0044] At the moment when the valve body 48 moves from a position away from the seat surface 44a to contact the seat surface 44a, a portion of the circumferential edge of the valve body 48 contacts the seat surface 44a. Therefore, in the low opening region, gas can pass between the portion of the circumferential edge of the valve body 48 that is not in contact with the seat surface 44a and the seat surface 44a, so the effective cross-sectional area of ​​the pressure regulating valve 41 is not zero.

[0045] In the low-opening region, when the opening of the pressure regulating valve 41 is changed to a small amount, the valve body 48 moves while pressing against the seat surface 44a. At this time, the sealing member 44 deforms under the pressure from the valve body 48. As a result, the smaller the opening of the pressure regulating valve 41 in the low-opening region, the larger the proportion of the peripheral edge of the valve body 48 that is in contact with the seat surface 44a, thus reducing the effective cross-sectional area of ​​the pressure regulating valve 41. When the opening of the pressure regulating valve 41 is fully closed, the entire peripheral edge of the valve body 48 is in contact with the seat surface 44a, and the effective cross-sectional area of ​​the pressure regulating valve 41 becomes 0 (zero).

[0046] As shown in Figure 2, the reduction mechanism 52 includes a gear 53. This gear 53 is one of several gears included in the reduction mechanism 52. The reduction mechanism 52 transmits the driving force of the motor 54 to the rotating shaft 51 via several gears, including the gear 53. This causes the rotating shaft 51 to rotate. In this way, the gear 53 rotates due to the drive of the motor 54, and this causes the valve body 48 to rotate.

[0047] The pressure regulating valve 41 is equipped with a spring (not shown) that biases the valve body 48 in the closing direction. The valve body 48 is held in a position where the force applied from the motor 54 to the rotating shaft 51 balances the force from the spring. The opening degree of the pressure regulating valve 41 can be adjusted by controlling the motor 54. The motor 54 is a DC motor.

[0048] The drive unit 55 drives the motor 54. More specifically, the drive unit 55 controls the rotational speed of the motor 54 by changing the voltage applied to the motor 54. The drive unit 55 uses pulse width modulation. The drive unit 55 includes a switching element 56. The switching element 56 is connected in series with the motor 54. The power source for the motor 54 is a secondary battery mounted on the industrial vehicle 10.

[0049] The opening degree sensor 58 detects the opening degree of the pressure regulating valve 41. For example, a Hall element can be used as the opening degree sensor 58. An encoder may also be used as the opening degree sensor 58.

[0050] The stopper 59 restricts the rotation of the gear 53. As the rotating shaft 51 is rotated in the direction that closes the valve body 48, the gear 53 and the stopper 59 come into contact. The rotation of the rotating shaft 51 is also restricted by the contact between the gear 53 and the stopper 59. In other words, the rotation of the valve body 48 in the direction that closes the valve body 48 stops at the position where the gear 53 comes into contact with the stopper 59. Fully closed pressure regulating valve 41 is the state in which the gear 53 comes into contact with the stopper 59.

[0051] <Department Head> As shown in Figure 1, the control unit 80 comprises a processor 81 and a storage unit 82. The storage unit 82 includes RAM (Random Access Memory) and ROM (Read Only Memory). The storage unit 82 stores program code or instructions configured to cause the processor 81 to execute processing. The storage unit 82, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The control unit 80 may be composed of hardware circuits such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The control unit 80, which is a processing circuit, may include one or more processors 81 that operate according to a computer program, one or more hardware circuits such as an ASIC or FPGA, or a combination thereof.

[0052] The control unit 80 controls the fuel cell unit 20. For example, the control unit 80 controls the output power [kW] of the fuel cell stack 21. The output power of the fuel cell stack 21 varies depending on the amount of cathode gas supplied to the fuel cell stack 21 and the amount of anode gas supplied to the fuel cell stack 21. The output power of the fuel cell stack 21 is the power generated by the fuel cell stack 21. The control unit 80 controls the amount of anode gas supplied to the fuel cell stack 21 by controlling the anode gas supply unit 62. The control unit 80 controls the amount of cathode gas supplied to the fuel cell stack 21 by controlling the electric compressor 32.

[0053] The control unit 80 controls the power generation of the fuel cell stack 21. The control unit 80 switches between a power generation state and a power generation stop state of the fuel cell stack 21. The power generation states include a low power generation state, a medium power generation state, and a high power generation state. By transitioning the power generation state of the fuel cell stack 21, the control unit 80 can change the power generated by the fuel cell stack 21 in steps.

[0054] The control unit 80 switches the power generation state of the fuel cell stack 21 by changing the target power E, which is the target value of the power generated by the fuel cell stack 21. The fuel cell stack 21 generates power while switching between multiple target powers E, including a first target power E1 and a second target power E2. Specifically, when controlling the fuel cell stack 21 to a high power generation state, the control unit 80 controls the target power E as the first target power E1. When controlling the fuel cell stack 21 to a medium power generation state, the control unit 80 controls the target power E as the second target power E2. When controlling the fuel cell stack 21 to a low power generation state, the control unit 80 controls the target power E as the third target power E3. The third target power E3 is smaller than the second target power E2. For example, the third target power E3 is 3 [kW]. For example, the second target power E2 is 5 [kW]. The second target power E2 is smaller than the first target power E1. For example, the first target power E1 is 8 [kW]. The control unit 80 changes the amount of cathode gas and the amount of anode gas supplied to the fuel cell stack 21 according to the target power E.

[0055] The control unit 80 controls, for example, the opening degree of the sealing valve 40. The control unit 80 can determine whether the key switch 13 is on or off. For example, if the key switch 13 is turned on, the control unit 80 is notified that the key switch 13 has been turned on from a vehicle control device (not shown) mounted on the industrial vehicle 10. Similarly, if the key switch 13 is turned off, the control unit 80 is notified that the key switch 13 has been turned off from the vehicle control device. This allows the control unit 80 to determine whether the key switch 13 is on or off.

[0056] As shown in Figure 2, the control unit 80 controls the opening degree of the pressure regulating valve 41 by moving the valve body 48. More specifically, the drive unit 55 switches the switching element 56 based on the pulse wave from the control unit 80. A pulse wave is a signal in which an ON signal and an OFF signal switch periodically. The proportion of the ON signal in one period of the pulse wave is called the duty cycle. The control unit 80 changes the voltage applied to the motor 54 by adjusting the duty cycle. The control unit 80 can adjust the opening degree of the pressure regulating valve 41 by driving the motor 54.

[0057] As shown in Figure 1, when the industrial vehicle 10 is turned off, the control unit 80 stops the power generation of the fuel cell stack 21 by stopping the supply of anode gas and cathode gas. The control unit 80 stops the supply of anode gas by sealing the anode internal flow path 26. Sealing of the anode internal flow path 26 is performed by keeping the exhaust drain valve 67 in a closed state.

[0058] The control unit 80 stops the supply of cathode gas by sealing the cathode internal flow path 23. Sealing of the cathode internal flow path 23 is performed by keeping the sealing valve 40 and the pressure regulating valve 41 in a closed state.

[0059] When the industrial vehicle 10 is ignited, the control unit 80 generates electricity for the fuel cell stack 21 by supplying anode gas and cathode gas. When cathode gas is supplied, the control unit 80 maintains the sealing valve 40 in an open state and adjusts the opening degree of the pressure regulating valve 41.

[0060] The control unit 80 adjusts the opening of the pressure regulating valve 41 so that the opening of the pressure regulating valve 41 decreases as the target power E of the fuel cell stack 21 increases. When the target power E of the fuel cell stack 21 is the first target power E1, the control unit 80 controls the opening of the pressure regulating valve 41 to the first opening A1 or less. For example, when the target power E of the fuel cell stack 21 switches from one of the second target power E2 or third target power E3 to the first target power E1, the control unit 80 changes the opening of the pressure regulating valve 41 to an opening within the low opening range. While the target power E of the fuel cell stack 21 is the first target power E1, the control unit 80 adjusts the opening of the pressure regulating valve 41 within the low opening range. As a result, the control unit 80 controls the opening of the pressure regulating valve 41 to the first opening A1 or less.

[0061] <Speed ​​control> In conjunction with adjusting the opening degree of the pressure regulating valve 41, the control unit 80 performs speed control. In speed control, the control unit 80 adjusts the movement speed of the valve body 48 according to the opening degree of the pressure regulating valve 41. The movement speed of the valve body 48 is the angular velocity [° / sec] of the pressure regulating valve 41. The control unit 80 determines the magnitude of the opening degree of the pressure regulating valve 41 based on the value detected from the opening degree sensor 58.

[0062] When the control unit 80 reduces the opening of the pressure regulating valve 41, it switches the movement speed of the valve body 48 to one of the first speed SP1, second speed SP2, and third speed SP3. Specifically, when the opening of the pressure regulating valve 41 is less than or equal to the first opening A1, the control unit 80 sets the movement speed of the valve body 48 to the first speed SP1. When the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2 (greater than the first opening A1), the control unit 80 sets the movement speed of the valve body 48 to the second speed SP2. When the opening of the pressure regulating valve 41 is greater than the first opening A1 and less than the second opening A2, the control unit 80 sets the movement speed of the valve body 48 to the third speed SP3.

[0063] The first opening degree A1 is the opening degree at which the valve body 48 contacts the seat surface 44a, and at which cathode gas flows between the valve body 48 and the seat surface 44a. The first opening degree A1 is the largest opening degree among the opening degrees of the pressure regulating valve 41 that are included in the low opening degree region.

[0064] The third speed SP3 is slower than the second speed SP2. The first speed SP1 is slower than both the second speed SP2 and the third speed SP3. Therefore, when the opening of the pressure regulating valve 41 is less than or equal to the first opening A1, the control unit 80 moves the valve body 48 at a speed slower than the speed at which the opening of the pressure regulating valve 41 is reduced when the opening is greater than the first opening A1. When the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2, the control unit 80 moves the valve body 48 at a speed faster than the speed at which the opening of the pressure regulating valve 41 is reduced when the opening is greater than the first opening A1 and less than the second opening A2.

[0065] In this embodiment, the control unit 80 sets the movement speed of the valve body 48 to the second speed SP2 when increasing the opening degree of the pressure regulating valve 41. That is, the control unit 80 moves the valve body 48 at the same speed when increasing the opening degree of the pressure regulating valve 41 and when decreasing the opening degree of the pressure regulating valve 41 when the opening degree of the pressure regulating valve 41 is 2 or higher. Therefore, when increasing the opening degree of the pressure regulating valve 41, the control unit 80 moves the valve body 48 at a faster speed than when decreasing the opening degree of the pressure regulating valve 41 when the opening degree of the pressure regulating valve 41 is 1 or lower.

[0066] Next, an example of the speed control processing procedure will be explained using Figure 5. The speed control processing shown in Figure 5 is repeated at predetermined intervals, for example, when the key is turned on. As shown in Figure 5, when speed control is started, the control unit 80 determines whether or not to reduce the opening degree of the pressure regulating valve 41 (step S110). If it is determined not to reduce the opening degree of the pressure regulating valve 41 (step S110: NO), the control unit 80 sets the movement speed of the valve body 48 to the second speed SP2 (step S120). Note that not reducing the opening degree of the pressure regulating valve 41 means either that the control unit 80 changes the opening degree of the pressure regulating valve 41 significantly, or that the control unit 80 does not change the opening degree of the pressure regulating valve 41. After performing the process in step S120, the control unit 80 terminates this control.

[0067] If the control unit 80 determines that it is necessary to reduce the opening of the pressure regulating valve 41 (step S110: YES), it determines whether the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2 (step S130). If the control unit 80 determines that the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2 (step S130: YES), it sets the movement speed of the valve body 48 to the second speed SP2 (step S120) and terminates this control.

[0068] If the control unit 80 determines that the opening of the pressure regulating valve 41 is less than the second opening A2 (step S130: NO), it determines whether the opening of the pressure regulating valve 41 is less than or equal to the first opening A1 (step S140). If the control unit 80 determines that the opening of the pressure regulating valve 41 is greater than the first opening A1 (step S140: NO), it sets the movement speed of the valve body 48 to the third speed SP3 (step S150). After performing the process in step S150, the control unit 80 terminates this control.

[0069] If the control unit 80 determines that the opening degree of the pressure regulating valve 41 is less than or equal to the first opening degree A1 (step S140: YES), it sets the movement speed of the valve body 48 to the first speed SP1 (step S160). After performing the process in step S160, the control unit 80 terminates this control.

[0070] <Relationship between the opening degree of the pressure regulating valve and the movement speed of the valve body> Figure 6 shows an example of the change in the opening degree of the pressure regulating valve 41. In Figure 6, the horizontal axis represents time, and the vertical axis represents the opening degree of the pressure regulating valve 41. This example describes the case where the pressure regulating valve 41 is adjusted from its fully open state (maximum opening degree Amax) to the target opening degree At.

[0071] At time t1, when the target opening degree At is set to a predetermined opening degree less than or equal to the first opening degree A1, the control unit 80 starts changing the opening degree of the pressure regulating valve 41 from the maximum opening degree Amax to the target opening degree At. While the opening degree of the pressure regulating valve 41 is greater than or equal to the second opening degree A2, the control unit 80 sets the movement speed of the valve body 48 to the second speed SP2, so that the valve body 48 moves at the second speed SP2.

[0072] When the opening of the pressure regulating valve 41 falls below the second opening A2, the control unit 80 sets the movement speed of the valve body 48 to the third speed SP3, causing the valve body 48 to move at the third speed SP3. This slows down the movement speed of the valve body 48. When the valve body 48 moves at the third speed SP3, the amount of change in the opening of the pressure regulating valve 41 per unit time is smaller than when the valve body 48 moves at the second speed SP2. The movement speed of the valve body 48 is maintained at the third speed SP3 until the opening of the pressure regulating valve 41 falls below the first opening A1.

[0073] At time t2, when the opening of the pressure regulating valve 41 falls below the first opening A1, the control unit 80 sets the movement speed of the valve body 48 to the first speed SP1, causing the valve body 48 to move at the first speed SP1. This slows down the movement speed of the valve body 48. When the valve body 48 moves at the first speed SP1, the amount of change in the opening of the pressure regulating valve 41 per unit time is smaller than when the valve body 48 moves at either the second speed SP2 or the third speed SP3. As long as the opening of the pressure regulating valve 41 is below the first opening A1, the movement speed of the valve body 48 is maintained at the first speed SP1.

[0074] At time t3, when the target opening degree At is set to the maximum opening degree Amax, the control unit 80 sets the movement speed of the valve body 48 to the second speed SP2, so that the valve body 48 moves at the second speed SP2. The control unit 80 changes the opening degree of the pressure regulating valve 41 to the maximum opening degree Amax.

[0075] [Operation of this embodiment] Next, the operation of this embodiment will be described. When the opening of the pressure regulating valve 41 is reduced in the low-opening region where the valve body 48 of the pressure regulating valve 41 is in contact with the seat surface 44a, the degree of change in the effective cross-sectional area is greater than when the opening of the pressure regulating valve 41 is reduced when the valve body 48 is not in contact with the seat surface 44a.

[0076] In this embodiment, when the opening of the pressure regulating valve 41 is reduced when the opening of the pressure regulating valve 41 is less than or equal to the first opening A1, the valve body 48 is moved at a slower speed than when the opening of the pressure regulating valve 41 is greater than the first opening A1. In the low opening region where the pressure regulating valve 41 is less than or equal to the first opening A1, the flow rate of cathode gas in the cathode flow path 30a changes as the opening of the pressure regulating valve 41 decreases, but by slowing down the movement speed of the valve body 48, the flow rate of cathode gas can be changed gradually.

[0077] [Effects of this embodiment] According to this embodiment, the following effects can be obtained. (1) When the opening of the pressure regulating valve 41 is less than or equal to the first opening A1, the control unit 80 moves the valve body 48 at a slower speed than when the opening of the pressure regulating valve 41 is greater than the first opening A1. Therefore, when the opening of the pressure regulating valve 41 is less than or equal to the first opening A1, the rapid change in the flow rate of cathode gas in the cathode flow path 30a that occurs as the opening of the pressure regulating valve 41 decreases can be suppressed.

[0078] (2) When the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2, which is greater than the first opening A1, the control unit 80 moves the valve body 48 at a faster speed than when the opening of the pressure regulating valve 41 is greater than the first opening A1 and less than the second opening A2. Therefore, when the opening of the pressure regulating valve 41 is reduced, the speed at which the valve body 48 is moved can be gradually reduced depending on whether the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2, greater than or equal to the first opening A1 and less than or equal to the first opening A1. Therefore, compared to the case where the speed at which the valve body 48 moves is changed in two stages, when the opening of the pressure regulating valve 41 is greater than the first opening A1 and when it is less than or equal to the first opening A1, the abrupt change in the flow rate of the cathode gas that accompanies a decrease in the opening of the pressure regulating valve 41 can be further suppressed.

[0079] (3) When the control unit 80 increases the opening of the pressure regulating valve 41, it moves the valve body 48 at a faster speed than when it decreases the opening of the pressure regulating valve 41 when the opening of the pressure regulating valve 41 is less than or equal to the first opening A1. Therefore, when increasing the opening of the pressure regulating valve 41, which is less likely to cause a sudden change in the flow rate of cathode gas in the cathode flow path 30a, the valve body 48 can be moved earlier, thereby improving the responsiveness of the opening change of the pressure regulating valve 41.

[0080] (4) The fuel cell stack 21 generates power by switching between multiple target powers E, including a first target power E1 and a second target power E2 which is smaller than the first target power E1. When the target power E is the first target power E1, the control unit 80 controls the opening of the pressure regulating valve 41 to a first opening A1 or less. By adjusting the movement speed of the valve body 48, abrupt changes in the flow rate of cathode gas in the cathode flow path 30a can be suppressed, so the target power E can be controlled by adjusting the opening of the pressure regulating valve 41 in a wider opening range that includes the opening range of the pressure regulating valve 41 below the first opening A1.

[0081] [Example of changes] The embodiment can be implemented with the following modifications. The embodiment and the following modifications can be combined with each other to the extent that they do not contradict the technical principles.

[0082] ○ The target power E of the fuel cell stack 21 may include one or more target powers E in addition to the first target power E1, the second target power E2, and the third target power E3. The target power E of the fuel cell stack 21 does not have to include the third target power E3. In short, the fuel cell stack 21 only needs to generate power by switching between multiple target powers E, including the first target power E1 and the second target power E2 which is smaller than the first target power E1.

[0083] ○ The target power E of the fuel cell stack 21 does not need to be switched between different values ​​such as a first target power E1 and a second target power E2; it may be a constant power. ○ As for the pressure regulating valve 41, any valve other than a butterfly valve, such as a globe valve or a ball valve, can be used, as long as the opening angle decreases as the valve body 48 approaches the seat surface 44a.

[0084] ○ When increasing the opening of the pressure regulating valve 41, the movement speed of the valve body 48 may be a speed less than the second speed SP2, such as the third speed SP3. When increasing the opening of the pressure regulating valve 41, the movement speed of the valve body 48 may be less than or equal to the first speed SP1.

[0085] ○ The control unit 80 may set the movement speed of the valve body 48 when reducing the opening degree of the pressure regulating valve 41 to one or more speeds other than the first speed SP1, second speed SP2, and third speed SP3. For example, when the opening degree of the pressure regulating valve 41 is greater than the first opening degree A1 and less than the second opening degree A2, the control unit 80 may change the movement speed of the valve body 48 to one of several speeds so that it slows down as the opening degree of the pressure regulating valve 41 decreases. For example, when the opening degree of the pressure regulating valve 41 is less than or equal to the first opening degree A1, the control unit 80 may change the movement speed of the valve body 48 to one of several speeds so that it slows down as the opening degree of the pressure regulating valve 41 decreases.

[0086] ○ When the opening of the pressure regulating valve 41 is reduced when the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2, and when the opening of the pressure regulating valve 41 is reduced when the opening of the pressure regulating valve 41 is greater than the first opening A1 and less than the second opening A2, the movement speed of the valve body 48 may be the same. In short, when the opening of the pressure regulating valve 41 is reduced when the opening of the pressure regulating valve 41 is less than or equal to the first opening A1, the valve body 48 should move at a slower speed than when the opening of the pressure regulating valve 41 is reduced when the opening of the pressure regulating valve 41 is greater than the first opening A1.

[0087] ○ The first speed SP1, the second speed SP2, and the third speed SP3 may be upper limits for the speed at which the valve body 48 moves. That is, the speed at which the valve body 48 moves may be controlled to be below these upper limits. In this case, when the opening of the pressure regulating valve 41 is reduced when the opening of the pressure regulating valve 41 is greater than or equal to the second opening A2, the lower limit of the speed at which the valve body 48 moves is set to a speed faster than the second speed SP2. When the opening of the pressure regulating valve 41 is reduced when the opening of the pressure regulating valve 41 is greater than the first opening A1 and less than the second opening A2, the lower limit of the speed at which the valve body 48 moves is set to a speed faster than the first speed SP1.

[0088] ○ Speed ​​control by the control unit 80 is not limited to when the key is turned on, but may also be performed by any operation by the user. For example, speed control may be performed by operating a lever, switch, push button, touch panel, etc. provided on the fuel cell unit 20.

[0089] ○ The fuel cell unit 20 may be installed in passenger cars, ships, trains, etc. ○ The fuel cell unit 20 may also be used as a stationary power generation device. The embodiment includes the configuration described in the following appendix.

[0090] <Note 1> A fuel cell stack that generates electricity through the reaction between the anode gas supplied to the anode channel and the cathode gas supplied to the cathode channel, A pressure regulating valve is provided downstream of the fuel cell stack in the cathode flow path, and its opening degree decreases as the valve body approaches the seat surface. A fuel cell unit having a control unit that moves the valve body to control the opening degree of the pressure regulating valve, The fuel cell unit is characterized in that the control unit moves the valve body at a speed slower when reducing the opening of the pressure regulating valve when the opening of the pressure regulating valve is less than or equal to a first opening, than at a speed slower when reducing the opening of the pressure regulating valve when the opening of the pressure regulating valve is greater than the first opening.

[0091] <Note 2> The fuel cell unit as described in Appendix 1, wherein the control unit moves the valve body at a speed faster than the speed at which it reduces the opening of the pressure regulating valve when the opening of the pressure regulating valve is greater than the first opening and less than the second opening, when the opening of the pressure regulating valve is greater than the first opening and less than the second opening.

[0092] <Note 3> The fuel cell unit according to Appendix 1 or Appendix 2, wherein when the control unit increases the opening of the pressure regulating valve, it moves the valve body at a faster speed than when it decreases the opening of the pressure regulating valve when the opening of the pressure regulating valve is less than or equal to the first opening.

[0093] <Note 4> The fuel cell unit according to any one of the following <Appendix 1> to <Appendix 3>, wherein the pressure regulating valve is a butterfly valve in which the valve body moves closer to the seat surface as the valve body rotates.

[0094] <Note 5> The fuel cell stack generates power while switching between multiple target powers, including a first target power and a second target power that is smaller than the first target power. The fuel cell unit according to any one of the following appendices: <Appendix 1> to <Appendix 4>, wherein the control unit controls the opening degree of the pressure regulating valve to be less than or equal to the first opening degree when the target power is the first target power. [Explanation of Symbols]

[0095] A1...First opening degree, A2...Second opening degree, E...Target power, E1...First target power, E2...Second target power, 20...Fuel cell unit, 21...Fuel cell stack, 30a...Cathode flow path, 41...Pressure regulating valve, 44a...Seat surface, 48...Valve body, 60a...Anode flow path, 80...Control unit.

Claims

1. A fuel cell stack that generates electricity through the reaction between the anode gas supplied to the anode channel and the cathode gas supplied to the cathode channel, A pressure regulating valve is provided downstream of the fuel cell stack in the cathode flow path, and its opening degree decreases as the valve body approaches the seat surface. A fuel cell unit having a control unit that moves the valve body to control the opening degree of the pressure regulating valve, The control unit, When the opening of the pressure regulating valve is less than or equal to the first opening, the speed at which the opening of the pressure regulating valve is reduced is slower than the speed at which the opening of the pressure regulating valve is reduced when the opening is greater than the first opening, by moving the valve body. A fuel cell unit characterized in that when increasing the opening of the pressure regulating valve, the valve body is moved at a faster speed than when decreasing the opening of the pressure regulating valve when the opening of the pressure regulating valve is less than or equal to the first opening.

2. The fuel cell unit according to claim 1, wherein the control unit moves the valve body at a speed faster than the speed at which it reduces the opening of the pressure regulating valve when the opening of the pressure regulating valve is greater than the first opening and less than the second opening, when the opening of the pressure regulating valve is greater than the first opening and less than the second opening.

3. The fuel cell unit according to claim 1, wherein the pressure regulating valve is a butterfly valve in which the valve body moves closer to the seat surface as the valve body rotates.

4. The fuel cell stack generates power while switching between multiple target powers, including a first target power and a second target power that is smaller than the first target power. The fuel cell unit according to claim 1, wherein the control unit controls the opening degree of the pressure regulating valve to be less than or equal to the first opening degree when the target power is the first target power.

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