Fuel cell system

Abstract

To provide a fuel cell system that suppresses the decline in power generation efficiency of a fuel cell.SOLUTION: The fuel cell system includes a fuel cell, a first injection valve having a first injection hole for injecting fuel gas, a second injection valve for injecting fuel gas and having a second injection hole larger than the first injection hole, an ejector mechanism through which the fuel gas injected from the first and second injection valves passes, a supply passage that supplies the fuel gas that has passed through the ejector mechanism to the fuel cell, a circulation passage that returns the fuel gas discharged from the fuel cell to the ejector mechanism, and a control device that controls the opening and closing states of the first and second injection valves in accordance with the required output to the fuel cell. The control device opens the second injection valve while continuing to inject the fuel gas from the first injection valve.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] There is known a fuel cell system equipped with first and second injection valves for injecting fuel gas. The first injection valve has a first injection hole, and the second injection valve has a second injection hole larger than the first injection hole. The fuel gas injected from either the first or second injection valve passes through an ejector. As a result, the fuel gas discharged from the fuel cell is recirculated to the fuel cell together with newly injected fuel gas (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-123458 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of the above-mentioned Patent Document 1, fuel gas is injected from either the first or second injection valve. For example, assume that the injection of fuel gas is switched from the first injection valve to the second injection valve while the fuel gas supplied to the fuel cell is kept constant. In this case, the pressure of the fuel gas injected from the second injection hole of the second injection valve, which is larger than the first injection hole, is lower than the pressure of the fuel gas injected from the first injection hole of the first injection valve. This reduces the flow rate of the fuel gas circulating through the fuel cell, and there is a risk of the power generation efficiency of the fuel cell decreasing.

[0005] It is therefore an object of the present invention to provide a fuel cell system that suppresses the decrease in power generation efficiency of the fuel cell. [Means for solving the problem]

[0006] The above object can be achieved by a fuel cell system comprising: a fuel cell; a first injection valve having a first injection hole for injecting fuel gas; a second injection valve having a second injection hole for injecting fuel gas and larger than the first injection hole; an ejector mechanism through which the fuel gas injected from each of the first and second injection valves passes; a supply passage for supplying the fuel gas that has passed through the ejector mechanism to the fuel cell; a circulation passage for returning the fuel gas discharged from the fuel cell to the ejector mechanism; and a control device for controlling the opening and closing states of each of the first and second injection valves in accordance with a required output for the fuel cell, wherein the control device opens the second injection valve while continuing to inject the fuel gas from the first injection valve. Effect of the Invention

[0007] It is possible to provide a fuel cell system in which a decrease in the power generation efficiency of the fuel cell is suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram of a fuel cell system. [Diagram 2] 4 is a flowchart illustrating a fuel gas injection control. [Diagram 3] 4 is a timing chart illustrating an example of fuel gas injection control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Fuel cell system configuration] 1 is a configuration diagram of a fuel cell system 1. The fuel cell system 1 is mounted on a vehicle, and includes an ECU (Electronic Control Unit) 3, a fuel cell (hereinafter referred to as FC) 4, an oxidant gas supply system 10, and a fuel gas supply system 20. The fuel cell system 1 is mounted on the vehicle. Electricity generated by the FC 4 is supplied to a motor that is a drive source for running the vehicle.

[0010] The FC4 is made up of a plurality of stacked solid polymer electrolyte type unit cells that generate power by receiving a supply of an oxidant gas and a fuel gas. A cathode flow path 4c through which the oxidant gas flows and an anode flow path 4a through which the fuel gas flows are formed in the FC4. The unit cell is composed of a membrane electrode assembly and a cathode side separator and an anode side separator that sandwich the membrane electrode assembly. The cathode flow path 4c is defined mainly between the membrane electrode assembly and the cathode side separator, and is a space through which the oxidant gas can flow. The anode flow path 4a is defined between the membrane electrode assembly and the anode side separator, and is a space through which the fuel gas can flow. The membrane electrode assembly includes an electrolyte membrane and catalyst layers formed on both sides of the electrolyte membrane.

[0011] The oxidant gas supply system 10 supplies air containing oxygen as an oxidant gas to the FC4, and includes a supply pipe 11, a discharge pipe 12, a bypass pipe 13, an air compressor 14, a bypass valve 15, an intercooler 16, and a back pressure valve 17. The supply pipe 11 is connected to the inlet of the cathode flow path 4c of the FC4. The discharge pipe 12 is connected to the outlet of the cathode flow path 4c of the FC4. The bypass pipe 13 communicates the supply pipe 11 and the discharge pipe 12. The bypass valve 15 is provided at the connection part between the supply pipe 11 and the bypass pipe 13. The bypass valve 15 switches the communication state between the supply pipe 11 and the bypass pipe 13. The air compressor 14, the bypass valve 15, and the intercooler 16 are arranged on the supply pipe 11 in this order from the upstream side. The back pressure valve 17 is arranged on the discharge pipe 12, upstream of the connection part between the discharge pipe 12 and the bypass pipe 13. The air compressor 14 supplies air containing oxygen as an oxidant gas to the FC4 via a supply pipe 11. The oxidant gas supplied to the FC4 is discharged via a discharge pipe 12. The intercooler 16 cools the oxidant gas supplied to the FC4. The back pressure valve 17 adjusts the back pressure on the cathode side of the FC4. The operation of the air compressor 14, the bypass valve 15, and the back pressure valve 17 is controlled by the ECU 3. The ECU 3 adjusts the opening of the bypass valve 15 and the back pressure valve 17 to adjust the flow rate of the oxidant gas supplied from the air compressor 14 to the FC4.

[0012] The fuel gas supply system 20 supplies hydrogen gas as a fuel gas to the FC4, and includes a tank 20T, a supply pipe 21, a circulation pipe 22, an exhaust pipe 23, a tank valve 24, a pressure adjusting valve 25, a small flow injector (hereinafter referred to as SINJ) 26a, a large flow injector (hereinafter referred to as LINJ) 26b, a gas-liquid separator 27, an exhaust valve 28, and a multi-nozzle ejector (hereinafter referred to as MEJ) 29. The tank 20T and the inlet of the anode flow path 4a of the FC4 are connected by a supply pipe 21. Hydrogen gas, which is a fuel gas, is stored in the tank 20T. The tank valve 24, the pressure adjusting valve 25, the SINJ 26a and the LINJ 26b, and the MEJ 29 are arranged in this order from the upstream side of the supply pipe 21. The SINJ 26a and the LINJ 26b are respectively provided at the portions of the supply pipe 21 where the supply pipe 21 partially branches off from each other. With the tank valve 24 open, the aperture of the pressure regulating valve 25 is adjusted, and either the SINJ 26a or the LINJ 26b is driven to inject fuel gas, and the fuel gas injected from either the SINJ 26a or the LINJ 26b passes through the MEJ 29 and is supplied to the FC 4. The portion of the supply pipe 21 downstream of the MEJ 29 is an example of a supply passage.

[0013] The SINJ 26a includes a valve seat having an injection hole 26a1 for injecting fuel gas, and a valve body driven by a solenoid to open and close the injection hole 26a1. Similarly, the LINJ 26b includes a valve seat having an injection hole 26b1 for injecting fuel gas, and a valve body driven by a solenoid to open and close the injection hole 26b1. The SINJ 26a and the LINJ 26b each inject fuel gas by opening the valve body by separating it from the valve seat for a predetermined time at a predetermined interval, and then stopping the injection of fuel gas by closing the valve body by abutting it against the valve seat for a predetermined time. In this case, the injection amount of fuel gas injected by one valve opening is changed by adjusting the duty ratio, which is the ratio of the valve opening period to the interval period. For example, when the duty ratio is 0%, the valve body is always in abutment with the valve seat and is in a fully closed state. When the duty ratio is 100%, the valve body is always in abutment with the valve seat and is in a fully open state. When the duty ratio is a predetermined value other than 0% and other than 100%, the valve disc repeatedly comes into contact with and separates from the valve seat, thereby repeatedly opening and closing the valve.

[0014] The injection hole 26b1 of the LINJ 26b is formed larger than the injection hole 26a1 of the SINJ 26a. Therefore, when the valve opening period is the same, the injection flow rate of the fuel gas from the LINJ 26b is larger than the injection flow rate of the fuel gas from the SINJ 26a. The injection flow rate of the fuel gas is the amount of the fuel gas injected from each injector per unit time. As described above, both the SINJ 26a and the LINJ 26b can change the injection amount of the fuel gas per opening by adjusting the duty ratio, but the upper limit value of the variable range of the injection amount of the LINJ 26b is set larger than the upper limit value of the variable range of the injection amount of the SINJ 26a. In this embodiment, as will be described later in detail, when there is a required output to the FC4, the fuel gas is controlled to be injected from the SINJ 26a or from both the SINJ 26a and the LINJ 26b. The SINJ 26a is an example of a first injection valve, and the LINJ 26b is an example of a second injection valve. The injection hole 26a1 is an example of a first injection hole, and the injection hole 26b1 is an example of a second injection hole. Note that a linear solenoid valve may be used instead of such an injector.

[0015] The circulation pipe 22 connects the outlet of the anode flow path 4a of the FC4 to the MEJ 29. A gas-liquid separator 27 is provided in the circulation pipe 22. The circulation pipe 22 is a pipe for returning the fuel gas to the FC4. When the fuel gas injected from the SINJ 26a or from both the SINJ 26a and the LINJ 26b passes through the MEJ 29, negative pressure is generated in the MEJ 29. The fuel gas discharged from the FC4 due to this negative pressure is sucked into the MEJ 29 via the gas-liquid separator 27. As a result, the fuel gas discharged from the FC4 is supplied again to the FC4. The MEJ29 is an example of an ejector mechanism. The circulation pipe 22 is an example of a circulation passage.

[0016] A discharge pipe 23 is connected to the gas-liquid separator 27. A discharge valve 28 is provided in the discharge pipe 23. The gas-liquid separator 27 separates and stores water from the fuel gas discharged from the FC4. When the discharge valve 28 opens, the water stored in the gas-liquid separator 27 is discharged to the outside of the fuel cell system 1 via the discharge pipe 23. The operation of the tank valve 24, the pressure regulating valve 25, the SINJ 26a, the LINJ 26b, and the discharge valve 28 is controlled by the ECU 3.

[0017] The ECU 3 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The accelerator opening sensor 6, the air compressor 14, the bypass valve 15, the back pressure valve 17, the tank valve 24, the pressure regulating valve 25, the SINJ 26a, the LINJ 26b, and the discharge valve 28 are electrically connected to the ECU 3. The ECU 3 calculates a required output to the FC4 based on the detection value of the accelerator opening sensor 6 and the driving states of the above-mentioned vehicle accessories and FC4 accessories. The ECU 3 also calculates a target current value of the FC4 according to the required output to the FC4, and controls the flow rates of the oxidant gas and the fuel gas supplied to the FC4 by the air compressor 14, the SINJ 26a, or the LINJ 26b so that the output current value of the FC4 becomes the target current value.

[0018] [Fuel gas injection control] The ECU 3 controls the SINJ 26a and the LINJ 26b based on the required output to the FC 4. FIG. 2 is a flowchart illustrating the fuel gas injection control. The ECU 3 determines whether the required output to the FC 4 has increased (step S1). If the answer is Yes in step S1, the ECU 3 increases the duty ratio of the SINJ 26a (step S2). Next, the ECU 3 determines whether the duty ratio of the SINJ 26a is 100% (step S3). If the answer is Yes in step S3, the ECU 3 increases the duty ratio of the LINJ 26b (step S4). If the answer is No in steps S1 and S3, the control ends.

[0019] FIG. 3 is a timing chart illustrating the fuel gas injection control. FIG. 3 shows the transition of the required output to FC4, the duty ratio of SINJ26a, and the duty ratio of LINJ26b. When the required output to FC4 is 0%, the duty ratios of SINJ26a and LINJ26b are maintained at 0% (time t0). When the required output to FC4 increases, the duty ratio of SINJ26a starts to increase while the duty ratio of LINJ26b is maintained at 0% (time t1). If the required output to FC4 is still increasing even when the duty ratio of SINJ26a becomes 100%, the duty ratio of LINJ26b starts to increase from 0% (time t2). When the required output to FC4 starts to decrease, the duty ratio of LINJ26b starts to decrease while the duty ratio of SINJ26a is maintained at 100% (time t3). If the required output to FC4 is decreasing when the duty ratio of LINJ26b becomes 0%, the duty ratio of SINJ26a starts to decrease from 100% (time t4). When the required output to FC4 becomes 0%, the duty ratio of SINJ26a also becomes 0% (time t5).

[0020] As described above, the SINJ 26a continues to inject fuel gas while the LINJ 26b opens. This makes it possible to prevent a decrease in the circulation flow rate of the fuel gas circulating through the FC 4. As a result, a decrease in the power generation efficiency of the FC 4 is prevented.

[0021] As described above, the opening of the LINJ 26b is controlled while the SINJ 26a is maintained fully open, to control the fuel gas supplied to the FC4. For example, if the opening of the LINJ 26b is controlled while the SINJ 26a is maintained at a predetermined opening other than fully open, the following problem may occur. In this case, the duty ratio of the SINJ 26a is controlled to a predetermined value other than 100%, and the SINJ 26a repeats opening and closing operations. As a result, the period during which the SINJ 26a repeats opening and closing operations may become longer, which may affect the durability of the SINJ 26a. In this embodiment, the SINJ 26a is maintained in a fully open state, and the opening and closing operations of the SINJ 26a are suppressed. Therefore, the effect on the durability of the SINJ 26a can be suppressed.

[0022] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0023] 1. Fuel cell system 3 ECU (control unit) 4 fuel cell 21 Supply pipe (supply passage) 22 Circulation pipe (circulation passage) 26a Small flow injector (first injection valve) 26b Large flow injector (second injection valve) 26a1 Injection hole (1st injection hole) 26b1 Injection hole (2nd injection hole) 29 Multi-nozzle ejector (ejector mechanism)

Claims

[Claim 1] A fuel cell; a first injection valve having a first injection hole for injecting fuel gas; a second injection valve that injects fuel gas and has a second injection hole that is larger than the first injection hole; an ejector mechanism through which the fuel gas injected from each of the first and second injection valves passes; a supply passage that supplies the fuel gas that has passed through the ejector mechanism to the fuel cell; a circulation passage for returning the fuel gas discharged from the fuel cell to the ejector mechanism; a control device that controls an open / close state of each of the first and second injection valves in response to a required output of the fuel cell; The control device opens the second injection valve while continuing the injection of the fuel gas from the first injection valve.

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