Fuel Cell Systems

Abstract

To make it possible to further suppress degradation in catalyst performance of fuel cells at low costs.SOLUTION: A fuel cell system 2 includes: a fuel cell 20 that generates electricity when an anode electrode 2A is supplied with fuel gas and a cathode electrode 2B is supplied with oxidant gas; a catalyst equipped on the anode electrode 2A; a fuel gas discharge section 35 connected to an outlet of fuel gas discharged from the anode electrode 2A; a first discharge section opening / closing valve 36 provided at the fuel gas discharge section 35; a pressurizing device 50 that pressurizes the anode electrode 2A; and a control section 61 that controls the opening and closing of the first discharge section opening / closing valve 36 and actuation of the pressurizing device 50. After the fuel cell 20 is stopped, the control section 61 actuates the pressurizing device 50 in a state in which the first discharge section opening / closing valve 36 is closed to pressurize the anode electrode 2A. The pressurizing device 50 pressurizes the anode electrode 2A by piston compression using pressure in a high-pressure fuel tank 30 storing fuel gas to be supplied to the anode electrode 2A.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel cell system suitable for use in a fuel cell vehicle or the like. [Background technology]

[0002] A fuel cell has an anode electrode (hydrogen electrode), a cathode electrode (oxygen electrode), and an electrolyte membrane disposed between these electrodes, and generates electricity by supplying a fuel gas to the anode electrode and an oxidizing gas to the cathode electrode. In such fuel cells, suppressing performance degradation has become an issue, and various technologies have been proposed.

[0003] For example, Patent Document 1 focuses on the fact that when a fuel cell vehicle is temporarily stopped and idling, the load on the fuel cell is small and the fuel cell continues to operate at a high cell voltage, which may cause the catalyst equipped on the cathode electrode to oxidize and deteriorate the catalyst performance. Patent Document 1 discloses a technology for suppressing deterioration of fuel cell performance by reducing the opening of the cathode back pressure valve during idling compared to the state before idling, thereby suppressing deterioration of catalyst performance.

[0004] Furthermore, Patent Documents 2 and 3 disclose a technology in which, when the operation of a fuel cell is stopped, compressed air generated by a compressor or the like is supplied to the anode electrode to scavenge the anode electrode and reduce the amount of moisture contained in the catalyst layer of the anode electrode, thereby suppressing catalyst deterioration due to water during shutdown or storage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-24889 A [Patent Document 2] JP 2009-104986 A [Patent Document 3] JP 2007-73328 A Summary of the Invention [Problem to be solved by the invention]

[0006] Meanwhile, while the techniques of Patent Documents 1 to 3 make it possible to suppress the deterioration of catalyst performance, there is a demand for further suppression of the deterioration of catalyst performance and for reducing the costs associated with suppressing the deterioration of catalyst performance.

[0007] The fuel cell system of the present invention was devised in view of the above problems, and one of its objectives is to further suppress the deterioration of the catalyst performance of the fuel cell at low cost. However, this objective is not the only objective, and another objective of the present invention is to achieve the effects that are derived from the configurations shown in the below-mentioned embodiments of the invention and that cannot be obtained by the conventional techniques. [Means for solving the problem]

[0008] The fuel cell system disclosed herein includes a fuel cell having an anode electrode, a cathode electrode, and an electrolyte membrane disposed between the anode electrode and the cathode electrode, the fuel cell generating power when a fuel gas is supplied to the anode electrode and an oxidizing gas is supplied to the cathode electrode, a catalyst provided in the anode electrode, a fuel gas discharge section communicating with an outlet for the fuel gas discharged from the anode electrode, a first discharge section on-off valve provided in the fuel gas discharge section, a pressurizing device that pressurizes the anode electrode, and a control section that controls the opening and closing of the first discharge section on-off valve and the operation of the pressurizing device. a fuel gas introduction passage communicating with an inlet of the anode electrode; The control unit operates the pressurizing device to pressurize the anode electrode with the first exhaust opening / closing valve closed after the fuel cell is stopped. The pressurizing device pressurizes the anode electrode by piston compression using the pressure in a high-pressure fuel tank that stores the fuel gas to be supplied to the anode electrode. The fuel cell includes a piston mechanism having a cylinder, a piston reciprocating within the cylinder, a first chamber defined by the piston on one side of the cylinder, and a second chamber defined by the piston on the other side of the cylinder and communicating with the fuel gas introduction passage, a first communication passage that communicates the first chamber with the high-pressure fuel tank, a second communication passage that communicates the second chamber with the high-pressure fuel tank, a first on-off valve interposed in the first communication passage, and a second on-off valve interposed in the second communication passage. Furthermore, the control unit causes the pressurizing device to perform a pressurizing operation with the first on-off valve opened and the second on-off valve closed after the fuel cell is stopped. . Effect of the Invention

[0009] According to the disclosed fuel cell system, after the fuel cell is stopped, the pressurizing device is operated to pressurize the anode electrode with the first exhaust valve closed, so that the electrode is efficiently pressurized. As a result, in the electrode that has been pressurized, the amount of saturated water vapor increases, promoting a decrease in humidity, and thus preventing deterioration of the catalyst due to water. In particular, since the anode electrode is pressurized by piston compression using the pressure in the high-pressure fuel tank, the equipment costs and operating costs associated with pressurization can be reduced. Therefore, deterioration of the catalyst performance of the fuel cell can be further prevented at low cost. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a configuration of a main part of an electric vehicle equipped with a fuel cell system according to an embodiment; [Diagram 2] 2 is a block diagram showing the configuration of a main part of the fuel cell system in FIG. 1 together with an ECU. [Diagram 3] 2 is a flowchart illustrating the control of the fuel cell system of FIG. [Figure 4] 4 is a flowchart illustrating the control of the opening degree of the pressure reducing valve in the control of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The structure of a fuel cell system according to an embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or application of techniques not explicitly described in the following embodiments. Each configuration of the embodiments can be modified in various ways without departing from the spirit of the embodiments. In addition, the configurations can be selected or combined as necessary.

[0012] [1. Configuration] The fuel cell system of this embodiment is equipped in an electric vehicle, and is characterized by its control of the fuel cell system, particularly the control after the fuel cell is stopped. Below, we will first explain the overall configuration of the electric vehicle and the fuel cell system, and then explain the control of the fuel cell system using a pressurizing device provided in the fuel cell system.

[0013] [1-1. Electric vehicles and fuel cell systems] As shown in Fig. 1, an electric vehicle 1 according to this embodiment is a so-called range extender electric vehicle in which power generated by a fuel cell 20 provided in a fuel cell system 2 is charged into a secondary battery 11, and a drive motor 12 is driven by the power of the secondary battery 11. The electric vehicle 1 includes a plug-in hybrid vehicle (PHEV) that can be externally charged or externally fed. The secondary battery 11 is a chargeable and dischargeable battery, and although there is no particular limitation, for example a lithium ion battery can be used.

[0014] The fuel cell 20 is a polymer electrolyte fuel cell that is supplied with hydrogen as a fuel gas and air as an oxidizing gas, and generates electricity through an electrochemical reaction between oxygen and hydrogen. There are no particular limitations on the specific configuration of the fuel cell 20, but here, the fuel cell 20 has a stack structure in which multiple cells are stacked with separators between them.

[0015] Each cell includes an anode electrode 2A (hydrogen electrode), a cathode electrode 2B (oxygen electrode), and an electrolyte membrane (in this embodiment, a solid polymer electrolyte membrane is used as an example) disposed between them. The anode electrode 2A is composed of an electrode catalyst layer in contact with the electrolyte membrane, and a gas diffusion layer provided on the electrode catalyst layer opposite the electrolyte membrane. Similarly, the cathode electrode 2B is also composed of an electrode catalyst layer and a gas diffusion layer. FIGS. 1 and 2 show the anode electrode 2A and the cathode electrode 2B in a schematic manner.

[0016] The electrode catalyst layer usually has catalytic activity for the electrode reactions at the anode electrode 2A and the cathode electrode 2B. Specifically, the electrode catalyst layer includes a catalyst supported on a carrier. The catalyst is not particularly limited as long as it has catalytic activity for the oxidation reaction of the fuel at the anode electrode 2A or the reduction reaction of the oxidant at the cathode electrode 2B, and any catalyst generally used in polymer fuel cells can be used. For example, platinum or an alloy with a metal (e.g., ruthenium, iron, nickel, manganese, cobalt, copper, etc.) can be used.

[0017] The support of the electrode catalyst layer of the cathode electrode 2B may be made of ceramics, and in particular, tin oxide is preferably used. Other ceramics that may be used include titanium oxide, niobium oxide, tantalum oxide, molybdenum oxide, and tungsten oxide. The support of the electrode catalyst layer of the anode electrode 2A may be made of ceramics, similar to the support of the cathode electrode 2B. In this embodiment, any of the above ceramics is used for the support of each electrode catalyst layer of the anode electrode 2A and the cathode electrode 2B. However, the support of each electrode catalyst layer is not limited to this, and for example, conductive carbon materials such as carbon particles such as carbon black and carbon fibers, and metal materials such as metal particles and metal fibers may also be used as the support.

[0018] A fuel cell 20 having such a cell is provided with an anode flow path (fuel gas flow path) consisting of a gas diffusion layer of the anode electrode 2A and a flow path communicating therewith, and a cathode flow path (oxidizing gas flow path) consisting of a gas diffusion layer of the cathode electrode 2B and a flow path communicating therewith, although details are not shown.

[0019] In addition to the fuel cell 20, the fuel cell system 2 includes a fuel gas flow system 3 connected upstream and downstream of the anode flow path on the anode electrode 2A side of the fuel cell 20, and an oxidizing gas flow system 4 connected upstream and downstream of the cathode flow path on the cathode electrode 2B side of the fuel cell 20.

[0020] The fuel gas distribution system 3 is connected in communication with, in order from upstream, a high-pressure fuel tank 30 (hereinafter referred to as "fuel tank 30") in which fuel gas (hydrogen gas) is stored, a fuel gas supply pipe 31, an anode flow path (not shown) on the anode electrode 2A side, and a fuel gas exhaust pipe 35 (fuel gas exhaust section).

[0021] The fuel gas supply pipe 31 is a flow path that connects the fuel tank 30 and the anode flow path. The fuel gas in the fuel tank 30 is supplied to the anode flow path through the fuel gas supply pipe 31. A main valve 32 and a pressure reducing valve 33 are interposed in the fuel gas supply pipe 31, in this order from the upstream side. The main valve 32 is a valve that opens and closes the opening of the fuel tank 30, and the pressure reducing valve 33 is a valve that reduces the pressure of the fuel gas supplied from the fuel tank 30 to a predetermined pressure to maintain a constant pressure. A pressurizing device 50 is interposed downstream of the pressure reducing valve 33, and a downstream end 37b of the fuel recirculation flow path 37 is connected in communication between the pressurizing device 50 and the inlet of the anode flow path.

[0022] The pressurizing device 50 pressurizes the inside of the fuel gas introduction passage 31a, which is the inlet side portion of the anode flow passage of the fuel gas supply pipe 31, by using the pressure in the fuel tank 30 under a predetermined condition, thereby pressurizing the inside of the anode flow passage and the inside of the cathode flow passage. In order to pressurize the inside of the cathode flow passage by the pressurizing device 50, a communication passage 39 (hereinafter also referred to as a "third communication passage 39") is connected in communication between the fuel gas supply pipe 31 and an oxidizing gas supply pipe 41 described later, and an opening / closing valve 39a (hereinafter also referred to as a "third opening / closing valve 39a") is interposed in the third communication passage 39. The third communication passage 39 is a component used for pressurization control described later. Details of the pressurizing device 50 and the third communication passage 39 will be described later.

[0023] The fuel gas discharge pipe 35 is a flow path through which the fuel gas discharged from the anode flow path flows. An anode back pressure valve 36 (an anode side dead end on-off valve serving as a first discharge section on-off valve) is interposed in the fuel gas discharge pipe 35. An upstream end 37a of a fuel recirculation flow path 37 is connected in communication between the outlet of the anode flow path and the anode back pressure valve 36.

[0024] The anode back pressure valve 36 is a control valve whose opening can be adjusted as desired, and can adjust the opening (flow path area) of the fuel gas exhaust pipe 35 as desired. By adjusting the opening of the anode back pressure valve 36, it is possible to adjust the pressure of the fuel gas supplied to the anode electrode 2A of the fuel cell 20. The anode back pressure valve 36 can, of course, be opened and closed, and also functions as an opening and closing valve.

[0025] The fuel recirculation flow path 37 is connected so as to communicate with an anode flow path outlet side portion of the fuel gas discharge pipe 35 and an anode flow path inlet side portion of the fuel gas supply pipe 31. In the fuel recirculation flow path 37, a gas-liquid separator (not shown), a recirculation dead-end opening / closing valve 37c, a recirculation pump 38, and a recirculation pump downstream valve 37d are interposed in this order from an upstream end 37a to a downstream end 37b.

[0026] Water produced by the electrochemical reaction in the anode flow path and fuel gas (hydrogen gas) that did not undergo electrochemical reaction are discharged to the fuel gas discharge pipe 35. The fuel gas containing this water is separated from the water in a gas-liquid separator, and is then passed through a fuel recirculation flow path 37, where it is pressurized to a predetermined pressure by a recirculation pump 38 and sent to the fuel gas supply pipe 31. At this time, the recirculation dead-end opening / closing valve 37c is opened, and the recirculation pump downstream valve 37d is used to adjust the amount of fuel gas that re-flows from the fuel recirculation flow path 37 into the fuel gas supply pipe 31.

[0027] The oxidizing gas flow system 4 is connected in communication with an air compressor 40, an oxidizing gas supply pipe 41, a cathode flow path (not shown) on the cathode electrode 2B side, and an oxidizing gas exhaust pipe 45 (oxidizing gas exhaust section) in this order from the upstream side. The air compressor 40 is a device that takes in outside air and pressurizes it to a predetermined pressure, and has a pressure adjustment function.

[0028] The oxidizing gas supply pipe 41 is a flow path that connects the air compressor 40 and the cathode flow path. In the oxidizing gas supply pipe 41, a humidified gas introduction valve 42, a humidifier 43, and a flow rate adjustment valve 44 are provided in this order from the upstream side. The humidified gas introduction valve 42 is a three-way switching valve, and can switch between a route for passing the outside air (air) pressurized to a predetermined pressure by the air compressor 40 through the humidifier 43 and a route for passing the air through a bypass path 43a without passing the air through the humidifier 43 (bypassing the humidifier 42). The reason why the introduced outside air is humidified by the humidifier 43 is to increase the conductivity of protons in the electrolyte membrane (solid polymer electrolyte membrane) by adding moisture to the air, thereby accelerating the electrochemical reaction.

[0029] The flow rate control valve 44 is a valve for adjusting the flow rate of the oxidizing gas supplied to the cathode side of the fuel cell 20. By adjusting the opening of this valve, outside air taken in from the air compressor 40 as the oxidizing gas is supplied to the cathode electrode 2B of the fuel cell 20 at a constant pressure.

[0030] The oxidizing gas exhaust pipe 45 is a flow path for exhaust gas exhausted from the cathode side of the fuel cell 20. The exhaust gas is discharged to the outside of the electric vehicle 1. The oxidizing gas exhaust pipe 45 is provided with a cathode back pressure valve 46 (a cathode side dead end opening / closing valve serving as a second exhaust section opening / closing valve). The cathode back pressure valve 46 is an adjustment valve whose opening degree can be adjusted as desired. By adjusting the opening degree of the cathode back pressure valve 46, it is possible to adjust the pressure of the oxidizing gas supplied to the cathode electrode 2B of the fuel cell 20. The cathode back pressure valve 46 can naturally be opened and closed, and also functions as an opening / closing valve.

[0031] In this embodiment, outside air that has been pressurized to a predetermined pressure by the air compressor 40 is introduced and supplied to the fuel cell 20 as oxidizing gas. However, a configuration may also be adopted in which a route for directly introducing outside air and a route for introducing outside air via the air compressor 40 are provided, and the oxidizing gas may be supplied to the fuel cell 20 by switching between these routes.

[0032] Such a fuel cell 20 is a fuel cell dedicated to power generation, and is connected to the secondary battery 11 via a DC / DC converter 14. DC power generated by the fuel cell 20 is converted to a predetermined voltage by the DC / DC converter 14 and charged to the secondary battery 11. The secondary battery 11 is also connected to the drive motor 12 via an inverter 13 and the DC / DC converter 14. The DC power charged to the secondary battery 11 is converted to AC power by the inverter 13 and supplied to the drive motor 12. The drive motor 12 generates a positive drive force (torque) for driving drive wheels (not shown) using the power from the secondary battery 11. The drive motor 12 also operates as a generator when decelerating the electric vehicle 1, such as during regenerative braking, and generates a negative regenerative force (torque). This regenerative power is converted to DC power by the inverter 13 and charged to the secondary battery 11.

[0033] The charge / discharge and drive control of the fuel cell 20, secondary battery 11 and drive motor 12 is performed by an ECU 60 (Electronic Control Unit), but as this is a well-known technique, a detailed description will be omitted. The ECU 60 is composed of a microcomputer equipped with a processor (central processing unit), a main memory device (main memory, storage, etc.), an interface device, etc. (not shown). The ECU 60 is capable of receiving detection signals from various sensors.

[0034] The fuel cell system 2 includes a control unit 61 that performs a predetermined pressurization control, in addition to the above-mentioned fuel cell 20, fuel gas distribution system 3, and oxidizing gas distribution system 4. The control unit 61 performs pressurization control by using a pressurizing device 50 under predetermined conditions to pressurize the inside of the anode flow path on the anode electrode 2A side and the inside of the cathode flow path on the cathode electrode 2B side.

[0035] The control unit 61 of this embodiment is provided as a part of the functions of a program executed by the ECU 60 (functional elements within the ECU 60), and is realized, for example, by software. However, the control unit 61 may be realized by hardware (electronic circuitry) separate from the ECU 60, or may be realized by a combination of software and hardware. The configuration of the pressurizing device 50 of this embodiment and the control of the pressurization in the anode flow channel and the cathode flow channel by the control unit 61 will be described below.

[0036] [1-2. Pressurizing device] 1 and 2, the pressurizing device 50 of the present embodiment includes a piston mechanism 51 provided immediately downstream of the pressure reducing valve 33, a communication passage 52 (hereinafter referred to as the "first communication passage 52"), and a communication passage 53 (hereinafter referred to as the "second communication passage 53"). That is, the pressurizing device 50 of the present embodiment is a device that pressurizes at least the anode electrode 2A by piston compression, and is also configured to be able to pressurize the cathode electrode 2B.

[0037] The piston mechanism 51 includes a cylinder 54, a piston 55 that reciprocates within the cylinder 54, a first chamber 56 defined by the piston 55 on one side (the fuel tank 30 side) within the cylinder 54, and a second chamber 57 defined by the piston 55 on the other side (the anode electrode 2A side) within the cylinder 54. The second chamber 57 communicates with the fuel gas introduction passage 31a.

[0038] The first communication passage 52 connects the first chamber 56 and the pressure reducing valve 33, and communicates between the first chamber 56 and the fuel tank 30 via the main valve 32 and the pressure reducing valve 33. The second communication passage 53 connects the second chamber 57 and the upstream portion of the first communication passage 52, and communicates between the second chamber 57 and the fuel tank 30 via the upstream portion of the first communication passage 52, the main valve 32, and the pressure reducing valve 33. These communication passages 52, 53 constitute a part of the fuel gas supply pipe 31.

[0039] An on-off valve 58 (hereinafter also referred to as "first on-off valve 58") is provided in the first communication passage 52, and on-off valves 59a, 59b (hereinafter also referred to as "second on-off valves 59a, 59b") are provided in the second communication passage 53. When there is no need to distinguish between the two second on-off valves 59a, 59b, they are referred to as "second on-off valves 59." In this embodiment, the second on-off valves 59a, 59b are provided at both ends of the second communication passage 53, but it is sufficient that at least one second on-off valve 59 is provided at any location in the second communication passage 53. During pressurization control, which will be described later, the on-off valves 58, 59a, 59b are appropriately switched.

[0040] [1-3. Control in fuel cell systems] A pressure sensor 71 for detecting the internal pressure Pa and a humidity sensor 73 for detecting the internal humidity Ha are provided in the anode flow path on the anode electrode 2A side of the fuel cell 20. A pressure sensor 72 for detecting the internal pressure Pc and a humidity sensor 74 for detecting the internal humidity Hc are provided in the cathode flow path on the cathode electrode 2B side of the fuel cell 20.

[0041] After the fuel cell 20 is stopped, the control unit 61 performs pressurization control to pressurize the inside of the anode flow path and the inside of the cathode flow path using the pressurizing device 50. Furthermore, if the fuel cell 20 is started during the pressurization control, the control unit 61 performs return control at the time of start-up. The return control is a control for preventing deterioration of hydrogen fuel efficiency by reusing the fuel gas (hydrogen) used in the piston compression.

[0042] The control unit 61 acquires detection signals from the above-mentioned sensors 71-74 and performs pressurization control based on the pressure Pa and humidity Ha in the anode flow path and the pressure Pc and humidity Hc in the cathode flow path. At this time, the control unit 61 performs pressurization control so that the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path increase to their respective target pressure ranges and the humidity Hc is maintained at or below a certain humidity. The target pressure range is a target (ideal) pressure range that can promote a decrease in humidity in each of the electrodes 2A, 2B.

[0043] Here, first target pressures Pa1, Pc1 are set as target values ​​to be achieved in the pressurization control according to the target pressure ranges of the pressures Pa and Pc, and second target pressures Pa2, Pc2 are set as start determination values ​​for the pressurization control. The first target pressures Pa1, Pc1 are set in advance as end conditions for the control to increase the opening degree of the pressure reducing valve 33 performed during the pressurization control, and are set to the upper limit of the target pressure range or a value corresponding to the upper limit so that the pressures Pa, Pc can be maintained within the target pressure range for a certain period of time without further increasing the opening degree of the pressure reducing valve 33. The second target pressures Pa2, Pc2 are set in advance as start conditions for the pressurization control, and are set to the lower limit of the target pressure range or a value corresponding to the lower limit.

[0044] During this pressurization control, the control unit 61 keeps the main valve 32 open, and opens and closes the pressure reducing valve 33, the on-off valves 58, 59a, 59b immediately downstream of the pressure reducing valve 33, the humidified gas introduction valve 42, the flow rate control valve 44, the on-off valve 39a that opens and closes the communicating passage 39, the recirculation dead-end on-off valve 37c, the recirculation pump downstream valve 37d, the anode back pressure valve 36, and the cathode back pressure valve 46 (at least two of these are collectively referred to as "valves" in Figures 1 and 2).

[0045] An example of pressurization control and return control performed by the control unit 61 will be described below with reference to the flowchart of Fig. 3. The flowchart shown in Fig. 3 is performed at a predetermined control period, for example, when the main power supply of the electric vehicle 1 is on. Note that a flag F is used in the following flowchart. The flag F is set to 1 when pressurization control using the pressurization device 50 is performed, and is set to 0 when pressurization control is not performed (including before the control starts). The control unit 61 continues to acquire detection signals from the sensors 71-74 while the flowchart is being performed.

[0046] 3, first, the control unit 61 judges whether the fuel cell 20 is in a stopped state (step S1). If the fuel cell 20 is in a stopped state, it judges whether the flag F is 0 (step S2). If the flag F is 1, the pressurization control has already been started and is being performed, so the flow returns and the control continues.

[0047] If the flag F is 0, it is determined whether the pressure Pa in the anode channel is lower than the second target pressure Pa2 (second pressure value) (Pa < Pa2) (step S3). As described above, the second target pressure Pa2 is a determination value preset as one of the start conditions for the pressure control. If it is determined that the pressure Pa in the anode channel is lower than the second target pressure Pa2, the flag F is set to 1 (step S7), and the pressure control is started (step S8).

[0048] Also, when the pressure Pa in the anode channel is not lower than the second target pressure Pa2, it is determined whether the pressure Pc in the cathode channel is lower than the second target pressure Pc2 (Pc < Pc2) (step S4). The second target pressure Pc2 is also a determination value preset as one of the start conditions for the pressure control as described above. Note that the second target pressures Pa2 and Pc2 on the anode side and the cathode side may be set according to the characteristics and properties of the respective electrodes 2A and 2B, and may be different or the same values. If it is determined that the pressure Pc in the cathode channel is lower than the second target pressure Pc2, the flag F is set to 1 (step S7), and the pressure control is started (step S8).

[0049] When both the pressure Pa in the anode channel and the pressure Pc in the cathode channel are not lower than the second target pressures Pa2 and Pc2, it is determined whether the humidity Ha in the anode channel is higher than the upper limit humidity Ha1 (Ha > Ha1) (step S5). If it is determined that the humidity Ha in the anode channel is higher than the upper limit humidity Ha1, the flag F is set to 1 (step S7), and the pressure control is started (step S8).

[0050] If the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path are not lower than the second target pressures Pa2 and Pc2, and the humidity Ha in the anode flow path is not higher than the upper limit humidity Ha1, it is determined whether the humidity Hc in the cathode flow path is higher than the upper limit humidity Hc1 (Hc>Hc1) (step S6). The upper limit humidity Ha1 and Hc1 on the anode side and the cathode side may be set according to the characteristics and properties of the electrodes 2A and 2B, for example, and may be different values ​​or the same value. If it is determined that the humidity Hc in the cathode flow path is higher than the upper limit humidity Hc1, the flag F is set to 1 (step S7), and the pressurization control is started (step S8). If the determination is "No" in all of steps S3 to S6, this flow is returned and the pressurization control is not started.

[0051] Therefore, when it is determined that either the pressure Pa in the anode flow path or the pressure Pc in the cathode flow path is lower than the second target pressure Pa2, Pc2, the first pressurization control is started. In addition, even if neither the pressure Pa in the anode flow path nor the pressure Pc in the cathode flow path is lower than the second target pressure Pa2, Pc2, when it is determined that either the humidity Ha in the anode flow path or the humidity Hc in the cathode flow path is higher than the upper limit humidity Ha1, Hc1, the pressurization control is started.

[0052] In the pressurization control, the pressure reducing valve 33 is opened to a reference opening degree, the second on-off valves 59a and 59b, the humidified gas introduction valve 42, the recirculation dead-end on-off valve 37c, the recirculation pump downstream valve 37d, the anode back pressure valve 36, and the cathode back pressure valve 46 are all closed, and the first on-off valve 58 is opened to ensure the fuel gas route R2 shown in FIG. 2. The route R2 is a piston compression line that introduces high-pressure fuel gas into the first chamber 56 during the pressurization control. In addition, the third on-off valve 39a that opens and closes the third communication passage 39 is opened. The reference opening degree of the pressure reducing valve 33 can be the default opening degree during the operation of the fuel cell 20. It is preferable to close the flow rate adjustment valve 44.

[0053] By opening the first on-off valve 58, high-pressure fuel gas flows into the first chamber 56 of the cylinder 54, and by pressing the piston 55, the second chamber 57 of the cylinder 54 is pressurized to the same pressure as the fuel gas. Then, the inside of the fuel gas inlet passage 31a communicating with the second chamber 57 is also pressurized, and through the third communication passage 39, the inside of the oxidizing gas inlet passage 41a of the oxidizing gas supply pipe 41 is also pressurized.

[0054] As a result, the inside of the anode flow passage on the anode electrode 2A side and the inside of the cathode flow passage on the cathode electrode 2B side are pressurized. Since the second on-off valves 59a, 59b on the upstream side of the anode flow passage are closed and the anode back pressure valve 36 on the downstream side of the anode flow passage is also closed (dead end), the compressed outside air sent to the inside of the anode flow passage is kept at high pressure without leaking. In addition, since the second on-off valves 59a, 59b on both ends of the second communication passage 53 are both closed, the inside of the second communication passage 53 is not unnecessarily pressurized and the pressure of the fuel gas can be efficiently utilized.

[0055] Meanwhile, the flow rate control valve 44 on the upstream side of the cathode flow path is closed, and the cathode back pressure valve 46 and the recirculation dead end opening / closing valve 37c on the downstream side of the cathode flow path are also closed, so that the fuel gas sent to the inside of the cathode flow path does not leak, and the inside of the cathode flow path is kept in a high pressure state. Inside the cathode flow path and anode flow path thus pressurized, the amount of saturated water vapor increases according to the pressurized state. Even if the amount of moisture inside the cathode flow path and the anode flow path does not decrease, the increase in the amount of saturated water vapor promotes a decrease in humidity. This pressurization control in step S8 continues as long as flag F is 1.

[0056] In this embodiment, during this pressurization control, if either of the pressures Pa, Pc detected by the pressure sensors 71, 72 does not reach the first target pressures Pa1, Pc1 within a predetermined time after starting the pressurization control, the control unit 61 performs opening control to increase the opening of the pressure reducing valve 33 by a predetermined opening.

[0057] Fig. 4 is an example of a flowchart for explaining the opening control of the pressure reducing valve 33 according to this embodiment. As shown in Fig. 4, first, in step S81, the counter value C is incremented, and then it is determined whether the counter value C has reached a target counter value C1 (step S82). The counter value C is incremented by 1 every control cycle, and the target counter value C1 is a determination value for determining the determination timing for determining whether the opening of the pressure reducing valve 33 should be increased.

[0058] In other words, when the counter value C reaches the target counter value C1, it means that a predetermined time (control period × C1) has elapsed since the start of counting. Normally, when pressurization control is started, it is assumed that the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path both rise and reach the first target pressures Pa1, Pc1 within the predetermined time. However, there may be cases where either the pressure Pa in the anode flow path or the pressure Pc in the cathode flow path does not reach the first target pressures Pa1, Pc1 even after the predetermined time has elapsed due to factors such as a low outside air temperature environment or a temperature drop caused by running wind. In this case, it is necessary to increase the opening of the pressure reducing valve 33 by a predetermined opening to promote pressurization.

[0059] If it is determined in step S82 that the counter value C is equal to or greater than the target counter value C1 (C has reached C1), the process proceeds to step S83, where it is determined whether the pressure Pa in the anode flow path is equal to or greater than the first target pressure Pa1. If the pressure Pa in the anode flow path is equal to or greater than the first target pressure Pa1, the process proceeds to step S84, where it is determined whether the pressure Pc in the cathode flow path is equal to or greater than the first target pressure Pc1.

[0060] If the pressure Pa in the anode flow path is equal to or greater than the first target pressure Pa1 and the pressure Pc in the cathode flow path is equal to or greater than the first target pressure Pc1, then the normal operation is carried out, and the opening degree of the pressure reducing valve 33 is not increased and is maintained, and this flow returns. On the other hand, if either the pressure Pa in the anode flow path or the pressure Pc in the cathode flow path has not reached the first target pressures Pa1, Pc1, the process proceeds to step S85, where the opening degree AP of the pressure reducing valve 33 is increased by a predetermined opening degree (small opening degree) ΔAP. Thereafter, the counter value C is reset to 0 (step S86), and this flow returns.

[0061] After the opening degree AP of the pressure reducing valve 33 is increased, a determination is again made after a predetermined time as to whether the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path have both reached the first target pressures Pa1, Pc1. In the same manner as above, if either the pressure Pa in the anode flow path or the pressure Pc in the cathode flow path has not reached the first target pressures Pa1, Pc1, the opening degree AP of the pressure reducing valve 33 is further increased by a predetermined opening degree (small opening degree) ΔAP.

[0062] In this way, in controlling the opening degree of the pressure reducing valve 33, unless both the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path reach the first target pressures Pa1, Pc1, the opening degree AP of the pressure reducing valve 33 is gradually increased and adjusted to the lower limit opening degree that can raise both the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path to the first target pressures Pa1, Pc1.

[0063] Returning to Fig. 3, when the fuel cell 20 is started from a stopped state, the process proceeds to step S9 based on the determination in step S1, and it is determined whether or not flag F is 1. If it is determined that flag F is 1, flag F is reset to 0 (step S10), and pressurization control is terminated (step S11). Then, in conjunction with the end of pressurization control, return control is implemented (step S12), and this flow returns.

[0064] To end the pressurization control following the start-up of the fuel cell 20, the pressure reducing valve 33 is opened to a reference opening (for example, a default opening), and the second on-off valves 59a, 59b are opened to ensure the fuel gas supply route R1 shown in FIG. 2. At this time, the anode back pressure valve 36 and the cathode back pressure valve 46 are both opened to the reference opening or the like, and the third on-off valve 39a that opens and closes the third communication passage 39 is closed. The route R1 is a reuse line that recovers the fuel gas used in the pressurization control during return control and reuses it for normal power generation. In the route R1, the fuel gas flows back through a part of the first communication passage 52 and into the second communication passage 53.

[0065] In the return control, the normal route R3 shown in Fig. 2 is secured, and the fuel gas used in the piston compression is circulated through the normal route R3 to prevent a deterioration in fuel efficiency. The normal route R3 is a line through which the fuel gas passes when the fuel cell 20 is operating. While the fuel cell 20 is operating, the first opening / closing valve 58 is closed, but in the return control, the first opening / closing valve 58 is held open for a predetermined time (a predetermined minute time) immediately after the start of the fuel cell 20, and then the first opening / closing valve 58 is closed. The humidified gas introduction valve 42 is opened appropriately based on a subsequent request for humidification, etc. The recirculation dead-end opening / closing valve 37c and the recirculation pump downstream valve 37d are also opened appropriately based on a subsequent request for fuel gas recirculation, etc.

[0066] That is, during the pressurization control, the second on-off valves 59a, 59b at both ends of the second communication passage 53 are both closed, and the inside of the second communication passage 53 is not pressurized. Therefore, the inside of the second communication passage 53 is at a lower pressure than the part between the pressure reducing valve 33 and the first on-off valve 58 of the fuel gas supply pipe 31 and the inside of the first chamber 56 of the cylinder 54. Therefore, when the second on-off valves 59a, 59b are opened, the fuel gas flows into the second communication passage 53 from the part between the pressure reducing valve 33 and the first on-off valve 58 of the fuel gas supply pipe 31. At this time, if the first on-off valve 58 is open, the fuel gas in the first chamber 56 also flows into the second communication passage 53.

[0067] It is considered that the fuel gas in the first chamber 56 flows into the second communication passage 53 for a short time immediately after the second on-off valves 59a, 59b are opened, and the fuel gas used in the piston compression can be circulated through the route R1 simply by holding the first on-off valve 58 in an open state for a predetermined very short time immediately after the second on-off valves 59a, 59b are opened. If the first on-off valve 58 is closed after the predetermined very short time has elapsed, the route R1 is closed, and only the normal route R3 needs to be used.

[0068] [2. Actions and Effects] (1) In the fuel cell system 2 according to the embodiment, after the fuel cell 20 is stopped, the pressurizing device 50 is operated to pressurize the inside of the anode flow path of the anode electrode 2A with the anode back pressure valve 36 serving as the anode side dead end on-off valve (first discharge section on-off valve) closed. This prevents pressure from escaping from the fuel gas discharge pipe 35, and allows the inside of the anode electrode 2A to be efficiently pressurized. As a result, in the anode electrode 2A which has become highly pressurized, the increase in the amount of saturated water vapor promotes a decrease in humidity, and deterioration of the catalyst due to water can be suppressed.

[0069] In this way, since low humidity can be efficiently promoted, costs can be reduced and catalyst deterioration of the fuel cell 20 can be further suppressed. Therefore, deterioration in performance and durability of the fuel cell 20 can be suppressed. In particular, since the anode electrode is pressurized by piston compression using the pressure inside the high-pressure fuel tank, equipment costs and operating costs related to pressurization (the use of a compressor requires energy costs for operation) can be suppressed.

[0070] The inhibition of catalyst degradation will be further explained. When the fuel cell 20 is stopped, the temperature inside the electrodes 2A, 2B drops thereafter, and some of the water vapor inside condenses to water. When water and oxygen are adsorbed onto the catalyst metal (for example, platinum Pt or an alloy of platinum Pt and a different metal), oxidation of the surface progresses, causing the catalyst to dissolve and become coarse, resulting in a deterioration in the power generation performance of the fuel cell and a decrease in the durability of the fuel cell. For this reason, while the fuel cell 20 is stopped, the power generation performance of the fuel cell and the durability of the fuel cell are likely to deteriorate.

[0071] In contrast, in the present fuel cell system 2, at least the inside of the anode electrode 2A is efficiently pressurized, so that the amount of saturated water vapor in the high-pressure anode electrode 2A increases, and the humidity reduction is promoted. When the humidity in the anode electrode 2A decreases, the condensation of water vapor in the anode electrode 2A is suppressed, and the increase in moisture in the anode electrode 2A is suppressed. This suppresses oxidation of the surface of the catalytic metal, and further suppresses deterioration in performance and durability of the fuel cell 20. Note that, according to the above-mentioned configuration in which the inside of the cathode electrode 2B is also pressurized, the same effect as that of the anode electrode 2A can be obtained on the cathode electrode 2B side.

[0072] (2) The pressurizing device 50 is configured to include a piston mechanism 51, a first communication passage 52, a second communication passage 53, a first on-off valve 58, and a second on-off valve 59. The control unit 61 can pressurize the pressurizing device 50 by opening the first on-off valve 58 and closing the second on-off valve 59. This makes it possible to utilize the pressure of the fuel gas in the fuel tank 30 at low cost.

[0073] (3) When the fuel cell 20 is started, the control unit 61 opens the second on-off valve 59 and closes the first on-off valve 58 after a predetermined time, thereby introducing the fuel gas in the first chamber 56 into the anode electrode 2A via the second chamber 57 and the fuel gas introduction path 31a. In this way, the fuel gas in the first chamber 56 used for pressurization can be reused for power generation, so that the fuel gas can be used without waste.

[0074] (4) When the pressure Pa of the anode electrode 2A detected by the pressure sensors 71, 72 does not reach the target pressure Pa1 during the pressurization control of the anode electrode 2A, the control unit 61 increases the aperture of the pressure reducing valve 33, so that the anode electrode 2A can be appropriately pressurized by utilizing the pressure in the fuel tank 30 to an extent required. In particular, in this embodiment, the aperture of the pressure reducing valve 33 is increased by small increments, so that utilization of the pressure in the fuel tank 30 can be easily minimized. Note that, according to the above-mentioned configuration in which the inside of the cathode electrode 2B is also pressurized, the same effect can be obtained on the cathode electrode 2B side.

[0075] (5) In addition, in the above fuel cell system 2 including the third communication passage 39 that communicates the fuel gas introduction passage 31a and the oxidizing gas introduction passage 41a, and the third on-off valve 39a provided in the third communication passage 39, the cathode electrode 2B is also pressurized. That is, the above control unit 61 operates the pressurizing device 50 to pressurize both the anode electrode 2A and the cathode electrode 2B while the anode back pressure valve 36 and the cathode back pressure valve 46 are closed (dead end), so that not only the anode electrode 2A but also the cathode electrode 2B can be efficiently pressurized. As a result, the humidity can be promoted by increasing the amount of saturated water vapor in the anode electrode 2A and the cathode electrode 2B, and deterioration of the catalyst due to water can be suppressed. Therefore, deterioration of the performance of the fuel cell 20 can be further suppressed.

[0076] (6) The fuel cell 20 is a power generating fuel cell mounted on the electric vehicle 1. Power generating fuel cells are stopped for a relatively long period of time, and therefore the deterioration of the catalyst due to water remaining or condensing on the electrodes 2A, 2B during the stopped period is likely to be accelerated accordingly. In contrast, the fuel cell system 2 can suppress such catalyst deterioration at low cost.

[0077] (7) The catalysts provided on the anode electrode 2A and the cathode electrode 2B of the fuel cell 20 are ceramic catalysts in which ceramics are used as carriers for the electrode catalyst layers. In the case of ceramic catalysts, applying pressure to the electrodes 2A, 2B increases the fuel cell resistance and makes it difficult for current to flow, suppressing the reaction of the residual gases at the electrodes 2A, 2B, which also suppresses catalyst deterioration.

[0078] (Other effects) In this embodiment, in controlling the opening degree of the pressure reducing valve 33, the opening degree of the pressure reducing valve 33 is increased until the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path both reach the first target pressures Pa1, Pc1, respectively. Therefore, by controlling the opening degree of the pressure reducing valve 33, the pressures in both the anode flow path and the cathode flow path can be increased to near the upper limits of the target pressure ranges.

[0079] In addition, in this embodiment, when either the pressure Pa in the anode flow path or the pressure Pc in the cathode flow path drops to the second target pressure Pa2, Pc2, pressurization control is started, so that both the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path can be maintained at or above the second target pressures Pa2, Pc2.

[0080] Furthermore, in this embodiment, as the start condition of the pressurization control, attention is paid not only to the pressure Pa in the anode flow path and the pressure Pc in the cathode flow path, but also to the humidity Ha in the anode flow path and the humidity Hc in the cathode flow path. That is, even if neither the pressure Pa in the anode flow path nor the pressure Pc in the cathode flow path has decreased to the second target pressures Pa2 and Pc2, when either the humidity Ha in the anode flow path or the humidity Hc in the cathode flow path has increased to the upper limit humidity Ha1 and Hc1, the pressurization control is started. Therefore, for example, in a situation where there is a lot of residual water and the humidity is high even if the pressures Pa and Pc have not decreased, the performance deterioration and durability deterioration of the catalyst are likely to occur, but such a problem can be avoided.

[0081] [3.Other] The above-described configuration of the fuel cell system 2 is merely an example, and the present invention is not limited to the above. For example, in the above embodiment, both the anode electrode 2A and the cathode electrode 2B are pressurized, but it is also possible to pressurize only the anode electrode 2A, in which case the third communication passage 39 and the third on-off valve 39a can be omitted.

[0082] In addition, the start and end conditions of the pressurization control and the specific method of controlling the opening degree of the pressure reducing valve 33 are not limited to those in the above embodiment, and may be set appropriately. For example, the conditions of the humidity Ha and Hc may be omitted. In this case, the humidity sensors 73 and 74 may also be omitted. In the above embodiment, a ceramic catalyst is used as the catalyst, but the catalyst is not limited to a ceramic catalyst. For example, a carbon catalyst using carbon as a carrier may also be used in this fuel cell system.

[0083] Furthermore, the fuel cell 20 is not limited to a fuel cell for generating electricity that is equipped on the electric vehicle 1, but may be a fuel cell for propulsion, or may be a fuel cell used for both generating electricity and propulsion. Furthermore, the present fuel cell system is not limited to being mounted on a vehicle. Furthermore, by combining the technology of the fuel cell system of the present invention with the conventional technologies described in, for example, Patent Documents 1 to 3, it is possible to further suppress the deterioration of the catalyst performance and the decrease in durability of the fuel cell at low cost. [Explanation of symbols]

[0084] 1 Electric vehicles 2. Fuel Cell System 2A Anode Electrode 2B Cathode electrode 20 Fuel Cell 30 High-pressure fuel tank 31a Fuel gas inlet 35 Fuel gas exhaust pipe (fuel gas exhaust section) 36 Anode back pressure valve (first discharge section opening / closing valve) 39 Third passageway 39a Third shutoff valve 41a Oxidizing gas inlet 45 Oxidizing gas exhaust pipe (Oxidizing gas exhaust section) 46 Cathode back pressure valve (second discharge section opening / closing valve) 50 Pressure device 51 Piston mechanism 52 First series of aisles 53 Second communication passage 54 Cylinder 55 Piston 56 Room 1 57 Second room 58 First shutoff valve 59, 59a, 59b Second opening and closing valve 61 Control section 71,72 Pressure Sensors Pa Pressure in the anode flow passage (pressure at the anode electrode) Pa1 First target pressure (first pressure value) Pa2 Second target pressure (second pressure value) Pc Pressure in the cathode flow passage (cathode electrode pressure) Pc1 First target pressure (first pressure value) Pc2 Second target pressure (second pressure value)

Claims

1. a fuel cell having an anode electrode, a cathode electrode, and an electrolyte membrane disposed between the anode electrode and the cathode electrode, the fuel cell generating power by supplying a fuel gas to the anode electrode and an oxidizing gas to the cathode electrode; A catalyst provided on the anode electrode; a fuel gas discharge portion communicating with an outlet of the fuel gas discharged from the anode electrode; a first discharge part opening / closing valve provided in the fuel gas discharge part; a pressure device for applying pressure to the anode electrode; A control unit that controls opening and closing of the first discharge unit opening / closing valve and operation of the pressurizing device; a fuel gas introduction passage communicating with the inlet of the anode electrode; the control unit operates the pressurizing device to pressurize the anode electrode while closing the first exhaust unit opening / closing valve after the fuel cell is stopped; The pressurizing device is The anode electrode is pressurized by piston compression using a pressure in a high-pressure fuel tank that stores a fuel gas to be supplied to the anode electrode, a piston mechanism including a cylinder, a piston reciprocating within the cylinder, a first chamber defined by the piston on one side within the cylinder, and a second chamber defined by the piston on the other side within the cylinder and communicating with the fuel gas introduction passage; a first communication passage communicating the first chamber with the high-pressure fuel tank; a second communication passage communicating the second chamber with the high-pressure fuel tank; a first on-off valve disposed in the first communication passage; a second on-off valve disposed in the second communication passage, The control unit causes the pressurizing device to perform a pressurizing operation after the fuel cell is stopped, with the first on-off valve being opened and the second on-off valve being closed. A fuel cell system comprising:

2. The control unit opens the second on-off valve when the fuel cell is started, and closes the first on-off valve after a predetermined time, thereby introducing the fuel gas in the first chamber into the anode electrode through the second chamber and the fuel gas introduction path.

2. The fuel cell system according to claim 1 .

3. a pressure reducing valve interposed between the high-pressure fuel tank and the pressurizing device; a pressure sensor that detects a pressure inside the anode electrode; The control unit increases an opening degree of the pressure reducing valve when the pressure detected by the pressure sensor does not reach a target pressure during control of pressurizing the anode electrode.

3. The fuel cell system according to claim 1 or 2, characterized in that:

4. A catalyst provided on the cathode electrode; an oxidizing gas exhaust portion communicating with an outlet for the oxidizing gas exhausted from the cathode; A second exhaust opening / closing valve provided in the oxidizing gas exhaust section; an oxidizing gas introduction passage communicating with an inlet of the cathode electrode; a third communication passage that communicates the fuel gas introduction passage and the oxidizing gas introduction passage; a third on-off valve provided in the third communication passage, After the fuel cell is stopped, the control unit closes the first exhaust unit on-off valve and the second exhaust unit on-off valve, and in a state in which the third on-off valve is opened, operates the pressurizing device to pressurize the anode electrode and the cathode electrode.

4. The fuel cell system according to claim 1, wherein the fuel cell system comprises:

5. The fuel cell is a fuel cell for generating electricity that is installed in a vehicle.

5. The fuel cell system according to claim 1, wherein the fuel cell system comprises:

6. The catalyst is a ceramic catalyst.

6. The fuel cell system according to claim 1, wherein the fuel cell system comprises:

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