Electrochemical cell system

Abstract

To provide an electrochemical cell system having air suppression control improved in readiness and durability of a bearing a compressor includes.SOLUTION: An electrochemical cell system 1 comprises: a case 10 covering an electrochemical cell stack 3 and including a suction port 12 and a discharge port 14; a fan 16 which is provided in the case; a first selector valve 31 provided in a third flow passage 23 which is a flow passage connecting the discharge port with a first flow passage 21; and a second selector valve 32 provided in a fourth flow passage 24 which is a flow passage connecting the discharge port with a second flow passage 22. As air suppression control of the electrochemical cell stack, actuation of an air compressor is stopped, and the first selector valve and the second selector valve are alternately opened or closed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to electrochemical battery systems. [Background technology]

[0002] Conventionally, electrochemical cells that generate electricity by chemically reacting hydrogen and oxygen are known. Fuel cells are one example of electrochemical cells. One application of fuel cells is a fuel cell system that supplies power to a vehicle's traction motor. In such a fuel cell system, air is supplied to the fuel cell stack by an air compressor.

[0003] Recently, a technology has been developed that suppresses deterioration of the fuel cell stack by restricting the supply of air to the fuel cell stack depending on the driving conditions, such as when the vehicle is traveling at low speeds, when stopped at traffic lights, etc. When the supply of air to the fuel cell stack is restricted, the output voltage of the fuel cell decreases over time, but if it decreases too much, it will not be possible to immediately output the voltage required for the next operation, even if the air supply is increased.

[0004] In response to this, Patent Document 1 discloses a technology that prevents the output voltage of a fuel cell from dropping too much by using intermittent control in which the rotation speed of the air compressor is reduced to reduce the air supply, and then the rotation speed of the air compressor is intermittently increased at specified timings. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2015 / 004508 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, the air supply is controlled by intermittently increasing the rotation speed of the air compressor, but frequent control of the rotation speed of the air compressor is slow to respond and has the problem of adversely affecting the durability of the air bearings that support the shaft of the air compressor.

[0007] For this reason, there has been a need for improved control over the supply of air to electrochemical cells.

[0008] An object of the present invention is to provide an electrochemical cell system having an air supply function that has improved responsiveness when the vehicle is running at low speeds and does not have the problem of durability of the bearings of the air compressor. [Means for solving the problem]

[0009] The electrochemical cell system according to the present invention an electrochemical cell stack (3') supplied with air and hydrogen to generate electricity; a case (10) for covering the electrochemical cell stack (3') and having an inlet (12) and an outlet (14); A fan (16) provided in the case (10); an air compressor (5) for supplying air to the electrochemical cell stack (3'); a first flow path (21) from the air compressor (5) to the electrochemical cell stack (3'); a second flow path (22) which is a flow path from the electrochemical cell stack (3') to the outside; a third flow path (23) that connects the outlet (14) and the first flow path (21); a fourth flow path (24) that connects the outlet (14) and the second flow path (22); a first switching valve (31) that opens or closes the third flow path (23); a second switching valve (32) that opens or closes the fourth flow path (24); a control device (50) that controls the operation of the fan (16), the air compressor (5), the first switching valve (31), and the second switching valve (32); In an electrochemical cell system (1') comprising: the control device (50) stops the operation of the air compressor (5) and alternately opens and closes the first switching valve (31) and the second switching valve (32) as an air suppression control for the electrochemical cell stack (3'); An electrochemical battery system (1'). Effect of the Invention

[0010] According to the present invention, it is possible to provide an electrochemical cell system having an air supply function that has improved responsiveness when the vehicle is running at low speeds and does not have the problem of durability of the bearings of the air compressor. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a schematic configuration of a fuel cell system according to an embodiment of the present invention. [Diagram 2] 1 is a block diagram showing the configuration of a control device used in a fuel cell system according to an embodiment of the present invention. [Diagram 3] 4 is a flowchart showing the operation of the fuel cell system according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. Note that the fuel cell stack is an example of an electrochemical cell stack, and the fuel cell system is an example of an electrochemical cell system. The configuration described below is an example of the present invention, and is not limited thereto.

[0013] Fig. 1 is a block diagram showing a schematic configuration of a fuel cell system 1 according to an embodiment of the present invention. The fuel cell system 1 shown in Fig. 1 has a fuel cell stack 3 that constitutes a fuel cell that generates electricity by chemically reacting hydrogen and oxygen. The fuel cell system 1 is an example of an electrochemical cell system 1' that has an electrochemical cell stack 3'.

[0014] The fuel cell stack 3 has a cathode and an anode, and generates electricity by supplying air to the cathode and hydrogen to the anode. In this embodiment, the fuel cell system 1 supplies power to a motor for driving a vehicle. Note that in this embodiment, illustrations and descriptions of a supply device and a supply path for supplying hydrogen to the fuel cell stack 3 are omitted.

[0015] The fuel cell system 1 has a case 10 that covers the entire fuel cell stack 3. The case 10 is provided with an intake port 12, an exhaust port 14, and a fan 16 that draws in outside air through the intake port 12 and exhausts the air to the outside of the case 10 through the exhaust port 14. The fan 16 is an electrically driven type of fan. The inside of the case 10 is ventilated by operation of the fan 16.

[0016] The fuel cell system 1 has an air compressor 5 that supplies air to the fuel cell stack 3. The air compressor 5 has an air foil bearing in the bearing that supports its rotating shaft, and is an electrically driven type of air compressor.

[0017] The fuel cell system 1 has a first flow path 21, a second flow path 22, a third flow path 23, and a fourth flow path 24, which are air flow paths. The first flow path 21 is a flow path having one end connected to the exhaust side of the air compressor 5 and the other end connected to the intake side of the fuel cell stack 3. The second flow path 22 is a flow path having one end connected to the exhaust side of the fuel cell stack 3 and the other end connected to the outside of the fuel cell system 1. The third flow path 23 is a flow path having one end connected to the exhaust port 14 of the case 10 and the other end connected to the middle of the first flow path 21. The fourth flow path 24 is a flow path having one end connected to the exhaust port 14 of the case 10 and the other end connected to the middle of the second flow path 22.

[0018] 1, the first flow path 21 and the second flow path 22 penetrate the case wall 18 of the case 10, but for example, the first flow path 21 may be configured to include a 1A flow path 21A from the air compressor 5 to the case wall 18 and a 1B flow path 21B from the case wall 18 to the fuel cell stack 3, with the 1A flow path 21A and the 1B flow path 21B being connected to each other by a flow path connector that penetrates the inside and outside of the case. The same applies to the second flow path 22 (2A flow path 22A, 2B flow path 22B).

[0019] In addition, although the third flow path 23 and the fourth flow path 24 are both connected to the exhaust port 14, as shown in FIG. 1, one end of the common flow path 25 may be connected to the exhaust port 14, and the other end of the common flow path 25 may be configured to be connected to the third flow path 23 and the fourth flow path 24.

[0020] A first switching valve 31 is provided in the third flow path 23, and a second switching valve 32 is provided in the fourth flow path 24. The first switching valve 31 and the second switching valve 32 are valves configured to be switchable between open and closed states by an electric signal.

[0021] The fuel cell system 1 has a control device 50. The control device 50 is configured to be able to electronically control the air compressor 5, the first switching valve 31, the second switching valve 32, the fan 16, and the like. The control device 50 is also configured to be able to acquire signals from various sensors and other control devices. The various sensors may include a voltage sensor 61 that detects the voltage E generated by the fuel cell stack 3, a vehicle speed sensor 63 that detects the vehicle speed V of the vehicle on which the fuel cell system 1 is mounted, an accelerator sensor 65 that detects the amount of accelerator depression A of the vehicle on which the fuel cell system 1 is mounted, and the like. The other control devices may also include a vehicle control device 51 that controls the vehicle on which the fuel cell system 1 is mounted, and the like.

[0022] The control device 50 is configured to be able to execute the air suppression control of the present invention. The air suppression control of the present invention is a control that suppresses the deterioration of the fuel cell stack 3 by suppressing the supply of air to the fuel cell stack 3 when the electric output taken from the fuel cell stack 3 is zero or a very small amount, such as when the vehicle is traveling at a low speed or when stopped at a traffic light. An example of a control that suppresses the supply of air is the intermittent control of the air compressor disclosed in Patent Document 1. However, frequently increasing and decreasing the rotation speed of the air compressor lacks responsiveness and has a problem of adversely affecting the durability of the air bearing that supports the shaft of the air compressor. The "air suppression control" of the present invention is a control that does not have the problems of the intermittent control of the air compressor described above when the vehicle is traveling at a low speed, and suppresses the deterioration of the fuel cell stack 3 by suppressing the supply of air to the fuel cell stack 3. In this application, the control that supplies air to the fuel cell stack 3 when the vehicle is not traveling at a low speed, etc., is called "normal air supply control" in contrast to the "air suppression control". In the "normal air supply control", air is supplied to the fuel cell stack 3 by the air compressor 5. On the other hand, in the "restricted air control", air is supplied to the fuel cell stack 3 without using the air compressor 5.

[0023] 2 shows an example of the configuration of the control device 50, in which the parts related to the control of the present invention are represented by functional blocks. This control device 50 is configured mainly with a known microcomputer, and has an acquisition unit 53, a control unit 55, and a judgment unit 57. Specifically, each of these units is realized by the execution of a program by the microcomputer.

[0024] In addition, the control device 50 is provided with memory elements such as a RAM (Random Access Memory) and a ROM (Read Only Memory), not shown, a timer counter, necessary electronic elements, electrical connection devices, and the like.

[0025] The acquisition unit 53 acquires signals from the voltage sensor 61, the vehicle speed sensor 63, the accelerator sensor 65, etc. The acquisition unit 53 may be configured to be able to acquire information from the vehicle control device 51.

[0026] The control unit 55 controls the operations of the air compressor 5, the first switching valve 31, the second switching valve 32, the fan 16, and the like.

[0027] The determination unit 57 makes a determination on signals from the voltage sensor 61, the vehicle speed sensor 63, the accelerator sensor 65, etc., the elapsed time, etc.

[0028] In normal air supply control, the control device 50 controls the operation of the air compressor 5 with the first switching valve 31 closed and the second switching valve 32 open. Air from the air compressor 5 is supplied to the fuel cell stack 3 via the first flow path. Air discharged from the fuel cell stack 3 is led to the outside of the fuel cell system 1 via the second flow path 22. In normal air supply control, air discharged from the exhaust port 14 by the operation of the fan 16 passes through the open second switching valve 32, and is led to the outside of the fuel cell system 1 via the fourth flow path 24 and the second flow path 22.

[0029] The control process in the embodiment of the present invention will be described below with reference to the flowchart in FIG.

[0030] The flow chart starts at step S100 and proceeds to step S110.

[0031] In step S110, the acquisition unit 53 acquires the vehicle speed V from the vehicle speed sensor 63, and in step S120, the judgment unit 57 judges whether the vehicle speed V is equal to or lower than a predetermined vehicle speed Vth (YES) or not (NO). If YES, the process proceeds to step S130 (air suppression control), and if NO, the air suppression control is not necessary, so the process proceeds to step S200, the flow ends, and the process transitions to or continues with normal air supply control. The predetermined vehicle speed Vth is the vehicle speed when the vehicle is stopped or moving slowly, for example, a vehicle speed of 10 km / hour or less. In step S120, the judgment unit 57 may judge whether the state in which the vehicle speed V is equal to or lower than the predetermined vehicle speed Vth continues for a predetermined time (YES) or not (NO).

[0032] As another embodiment, in step S110, the acquisition unit 53 acquires the accelerator depression amount A from the accelerator sensor 65, and in step S120, the judgment unit 57 may judge whether the accelerator depression amount A is equal to or less than a predetermined depression amount Ath (YES) or not (NO). If YES, the process proceeds to step S130 (air suppression control), and if NO, the air suppression control is not necessary, so the process proceeds to step S200, the flow is ended, and the process proceeds to or continues with normal air supply control. The predetermined depression amount Ath is, for example, when the accelerator is in an idling position. In addition, in step S120, the judgment unit 57 may judge whether the state in which the accelerator depression amount A is equal to or less than a predetermined depression amount AVth continues for a predetermined time (YES) or not (NO).

[0033] Furthermore, as another embodiment, in step S110, the acquisition unit 53 may acquire the required output P for the fuel cell system 1 calculated by the vehicle control device 51, and in step S120, the judgment unit 57 may judge whether the required output P is smaller than a predetermined required output Pth (YES) or not (NO). If YES, the process proceeds to step S130 (air suppression control), and if NO, air suppression control is not necessary, so the process proceeds to step S200, where the flow is ended, and the process transitions to or continues with normal air supply control.

[0034] In step S130, the control unit 55 stops the air compressor 5 or confirms that the air compressor 5 is stopped. Furthermore, if the fan 16 is not operating, the fan 16 is operated, and the process proceeds to step S140. Here, the air compressor 5 is stopped, and the supply of air from the air compressor 5 to the fuel cell stack 3 is stopped. Furthermore, since the first switching valve 31 is closed and the second switching valve 32 is open, the air discharged from the exhaust port 14 by the operation of the fan 16 is discharged to the outside via the fourth flow path 24 and the second flow path 22. As a result, the amount of air remaining in the fuel cell stack 3 decreases, and the voltage E generated by the fuel cell stack 3 drops.

[0035] In step S140, the acquisition unit 53 acquires the voltage E generated by the fuel cell stack 3 from the voltage sensor 61, and the process proceeds to step S150.

[0036] In step S150, the determination unit 57 determines whether the voltage E is equal to or lower than the lower voltage Eth_lower (YES) or not (NO). If YES, proceed to step S160, and if NO, return to step S140. The lower voltage Eth_lower is, for example, a voltage below which, if the voltage falls below this level, it will not be possible to immediately output the voltage required for the next operation even if the air supply is subsequently increased, or a voltage higher than this voltage by a predetermined value.

[0037] In step S160, the control unit 55 opens the first switching valve 31 and closes the second switching valve 32, and proceeds to step S170. As a result, the air sent by the fan 16 is supplied to the fuel cell stack 3 via the third flow path 23 and the first flow path 21, and the voltage E changes from decreasing to increasing.

[0038] In step S170, the acquisition unit 53 acquires the voltage E generated by the fuel cell stack 3 from the voltage sensor 61, and the process proceeds to step S180.

[0039] In step S180, the judgment unit 57 judges whether the voltage E is higher than the upper voltage Eth_upper (YES) or not (NO). If YES, proceed to step S190, and if NO, return to step S170. The upper voltage Eth_upper is, for example, a voltage above which deterioration of the fuel cell stack 3 is accelerated, or a voltage lower than this voltage by a predetermined value. The upper voltage Eth_upper is a higher value than the lower voltage Eth_lower.

[0040] In step S190, the control unit 55 opens the first switching valve 31 and closes the second switching valve 32, and the process returns to step S110. As a result, air is discharged to the outside via the fourth flow path 24 and the second flow path 22, so that the supply of air to the fuel cell stack 3 stops and the voltage E changes from increasing to decreasing.

[0041] The above flow may include controlling the rotation speed of the fan 16. For example, when it is determined that the voltage E is rising slowly, the rotation speed of the fan 16 may be increased, and when it is determined that the voltage E is rising quickly, the rotation speed of the fan 16 may be decreased. When normal air supply control is resumed after the result of NO in step 120 and the flow is terminated in step 200, the first switching valve 31 may be opened and the second switching valve 32 may be closed until air supply by the air compressor 5 is started, and the required air may be supplied by the operation of the fan 16. When air supply by the air compressor 5 is started, the first switching valve 31 is closed and the second switching valve 32 is opened.

[0042] According to this embodiment, air suppression control is performed that does not require air supply from the air compressor 5 when the vehicle is traveling at low speeds, etc., so that it is possible to suppress deterioration of the fuel cell stack 3, and it is possible to provide a fuel cell system 1 (electrochemical cell system 1') that does not need to take into account the responsiveness of the air compressor 5 during control and does not have any durability issues with the foil bearings of the air compressor 5.

[0043] [Variations] In the embodiment described above, during air suppression control, the voltage E generated by the fuel cell stack 3 is detected, and the first and second switching valves 31 and 32 are alternately opened and closed so that this voltage E has a value between the lower voltage Eth_lower and the upper voltage Eth_upper. In the modified example, a switching time is determined in advance for the voltage E generated by the fuel cell stack 3 to have a value between the lower voltage Eth_lower and the upper voltage Eth_upper. Then, during air suppression control, the first and second switching valves 31 and 32 are alternately opened and closed based on this switching time.

[0044] For example, the switching time can be determined such that the time when the first switching valve 31 is closed and the second switching valve 32 is opened is t1, and the time when the first switching valve 31 is opened and the second switching valve 32 is closed is t2. During the air suppression control, the control unit 55 closes the first switching valve 31 and opens the second switching valve 32 for the time t1, and then opens the first switching valve 31 and closes the second switching valve 32 for the time t2. By repeating this, the voltage E can be maintained at a value between the lower voltage Eth_lower and the upper voltage Eth_upper. In addition, the switching time may be changed based on the temperature and pressure in the case 10. This is because the amount of air supplied to the fuel cell stack 3 changes depending on the temperature and pressure in the case 10.

[0045] According to the modified example of this embodiment, when the vehicle is traveling at low speeds, etc., air suppression control is performed that does not require air supply from the air compressor 5, making it possible to provide a fuel cell system 1 (electrochemical cell system 1') that can suppress deterioration of the fuel cell stack 3, does not need to take into account the responsiveness of the air compressor 5 during control, and does not have durability issues with the foil bearings of the air compressor 5. Furthermore, since it is not necessary to control based on the voltage E generated by the fuel cell stack 3, the air suppression control can be made simpler. [Explanation of symbols]

[0046] 1 fuel cell system, 1' electrochemical cell system, 3 fuel cell stack, 3' electrochemical cell stack, 5 air compressor, 10 case, 12 intake port, 14 exhaust port, 16 fan, 18 case wall, 21 first flow path, 22 second flow path, 23 third flow path, 24 fourth flow path, 31 first switching valve, 32 second switching valve, 50 vehicle control device, 51 control device, 61 voltage sensor, 63 speed sensor, 65 accelerator sensor

Claims

1. an electrochemical cell stack (3') supplied with air and hydrogen to generate electricity; a case (10) for covering the electrochemical cell stack (3') and having an inlet (12) and an outlet (14); A fan (16) provided in the case (10); an air compressor (5) for supplying air to the electrochemical cell stack (3'); a first flow path (21) from the air compressor (5) to the electrochemical cell stack (3'); A second flow path (22) which is a flow path from the electrochemical cell stack (3') to the outside; a third flow path (23) that connects the outlet (14) and the first flow path (21); a fourth flow path (24) that connects the outlet (14) and the second flow path (22); a first switching valve (31) that opens or closes the third flow path (23); a second switching valve (32) that opens or closes the fourth flow path (24); a control device (50) that controls the operation of the fan (16), the air compressor (5), the first switching valve (31), and the second switching valve (32); In an electrochemical cell system (1') comprising: The control device (50) performs air suppression control of the electrochemical cell stack (3') by stopping the operation of the air compressor (5) and alternately opening and closing the first switching valve (31) and the second switching valve (32). An electrochemical cell system (1').

2. the control device (50) alternately opens or closes the first switching valve (31) and the second switching valve (32) based on a voltage (E) generated by the electrochemical cell stack (3'); Electrochemical cell system (1') according to claim 1.

3. The control device (50) alternately opens or closes the first switching valve (31) and the second switching valve (32) based on a predetermined switching time. Electrochemical cell system (1') according to claim 1.

Images