Fuel cell system

Abstract

This invention provides a fuel cell system that improves the lifespan of the fuel gas injector. [Solution] The fuel cell system 1 includes an injector 26a that injects fuel gas into a fuel cell 4 and a linear solenoid valve 26b that has a larger injection flow rate than the injector 26a. The control device 3 consists of a switching unit that operates the injector 26a when the required power generation is less than a switching value and operates the linear solenoid valve 26b when it is equal to or greater than the switching value; an operation control unit that operates the injector 26a when the fuel gas supply pressure falls below a lower limit and stops the operation of the injector 26a when the pressure rises above an upper limit; an accumulation unit that accumulates the number of times the injector 26a operates; and a reduction control unit that performs reduction control to reduce the number of times the injector 26a operates when the number of times it operates exceeds a threshold, compared to when the number of times it operates is less than the threshold.

Description

Technical Field

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

Background Art

[0002] There is a fuel cell system including a fuel cell, an injector that injects fuel gas into the fuel cell, and a linear solenoid valve that injects fuel gas into the fuel cell and has a larger fuel gas injection flow rate than the injector (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the number of operating times of the injector becomes excessive, the life of the injector may be reduced.

[0005] Therefore, an object is to provide a fuel cell system with improved life of an injector that injects fuel gas.

Means for Solving the Problems

[0006] The above objective can be achieved by a fuel cell system comprising: a fuel cell; an injector for injecting fuel gas into the fuel cell; a linear solenoid valve for injecting fuel gas into the fuel cell, with a fuel gas injection flow rate greater than that of the injector; and a control device for controlling the injector and the linear solenoid valve, wherein the control device includes: a switching unit that activates the injector when the required power generation of the fuel cell is less than a switching value, and activates the linear solenoid valve when the required power generation is equal to or greater than the switching value; an operation control unit that activates the injector when the supply pressure of the fuel gas supplied to the fuel cell falls below a lower limit when the required power generation is less than the switching value, and stops the operation of the injector when the pressure rises above an upper limit; an accumulation unit that accumulates the number of times the injector operates; and a reduction control unit that, when the number of operations exceeds a threshold, performs reduction control to reduce the number of times the injector operates compared to when the number of operations is less than the threshold.

[0007] The reduction control may change the upper limit to a higher value while maintaining the lower limit when the number of operations exceeds the threshold, compared to when the number of operations is below the threshold.

[0008] The reduction control may change the switching value to a lower value than when the number of operations is less than the threshold value if the number of operations exceeds the threshold value.

[0009] The reduction control may, when the number of operations exceeds the threshold, change the upper limit to a higher value while maintaining the lower limit, and change the switching value to a lower value, compared to when the number of operations is below the threshold.

[0010] The control device may include a notification control unit that notifies when the number of operations exceeds the threshold. [Effects of the Invention]

[0011] This allows us to provide fuel cell systems with improved lifespan for the fuel gas injectors. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram illustrating the configuration of a fuel cell system. [Figure 2] This flowchart illustrates the reduction control performed by the ECU. [Figure 3] This is a timing chart illustrating the process of changing the upper limit. [Figure 4] This is a timing chart illustrating the process of changing the switching value. [Modes for carrying out the invention]

[0013] [Fuel cell system configuration] Figure 1 is a diagram of the 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 oxidizer gas supply system 10, and a fuel gas supply system 20. The fuel cell system 1 is mounted on a vehicle. The electricity generated by the FC 4 is supplied to the motor, which is the driving source of the vehicle.

[0014] FC4 consists of multiple stacked solid polymer electrolyte single cells that generate electricity by receiving oxidant gas and fuel gas. Within FC4, a cathode channel 4c through which the oxidant gas flows and an anode channel 4a through which the fuel gas flows are formed. A single cell consists of a membrane electrode assembly and a cathode-side separator and an anode-side separator that sandwich it. The cathode channel 4c is mainly defined between the membrane electrode assembly and the cathode-side separator and is a space through which the oxidant gas can flow. The anode channel 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.

[0015] The oxidizer gas supply system 10 supplies oxygen-containing air as the oxidizer 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 connects the supply pipe 11 and the discharge pipe 12. The bypass valve 15 is provided at the connection point between the supply pipe 11 and the bypass pipe 13. The bypass valve 15 switches the connection 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 order from upstream. The back pressure valve 17 is located on the discharge pipe 12, upstream of the connection point between the discharge pipe 12 and the bypass pipe 13. The air compressor 14 supplies oxygen-containing air as an oxidizing gas to the FC4 via the supply pipe 11. The oxidizing gas supplied to the FC4 is discharged via the discharge pipe 12. The intercooler 16 cools the oxidizing 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 flow rate of the oxidizing gas supplied from the air compressor 14 to the FC4 is adjusted by adjusting the opening of the bypass valve 15 and the back pressure valve 17 via the ECU 3.

[0016] The fuel gas supply system 20 supplies hydrogen gas as fuel gas to the FC4 and includes a tank 20T, a supply pipe 21, a circulation pipe 22, a discharge pipe 23, a tank valve 24, a pressure regulating valve 25, an injector (hereinafter referred to as INJ) 26a, a linear solenoid valve (hereinafter referred to as LSV) 26b, a pressure sensor S, a gas-liquid separator 27, a discharge 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 the supply pipe 21. The tank 20T stores hydrogen gas, which is the fuel gas. The tank valve 24, pressure regulating valve 25, INJ 26a and LSV 26b, and MEJ 29 are arranged in order from the upstream side of the supply pipe 21. INJ 26a and LSV 26b are provided at the partially branched sections of the supply pipe 21, respectively. The pressure sensor S detects the supply pressure P of the fuel gas supplied to the FC4 from at least one of the INJ26a and LSV26b. The supply pressure P is the pressure in the supply pipe 21 downstream of the INJ26a and LSV26b. The supply pressure P corresponds to the pressure at the inlet of the FC4. With the tank valve 24 open, the opening of the pressure regulating valve 25 is adjusted. At least one of the INJ26a and LSV26b is driven to inject fuel gas. The injected fuel gas passes through the MEJ29 and is supplied to the FC4.

[0017] INJ26a is an on / off valve that intermittently injects hydrogen gas by controlling the nozzle opening to only two positions: fully closed and fully open. The diameter of the INJ26a's nozzle is smaller than that of the LSV26b's nozzle. Consequently, the injection flow rate of INJ26a is lower than that of LSV26b. Injection flow rate refers to the amount of fuel gas injected per unit time.

[0018] The LSV26b is a valve that opens and closes the injection port by driving a linear solenoid. The LSV26b is controlled to maintain the opening of the injection port at a predetermined opening between the fully closed and fully open positions. In this way, the fuel gas injection flow rate from the LSV26b is adjusted to a predetermined amount. The opening of the LSV26b is adjusted according to the power generation W required by the FC4.

[0019] The circulation pipe 22 connects the outlet of the anode flow path 4a of FC4 and the MEJ29. A gas-liquid separator 27 is provided in the circulation pipe 22. The circulation pipe 22 is a pipe for refluxing fuel gas to FC4. When the fuel gas injected from at least one of INJ26a and LSV26b passes through the MEJ29, a negative pressure is generated in the MEJ29. Due to this negative pressure, the fuel off-gas discharged from FC4 is sucked into the MEJ29 through the gas-liquid separator 27. Thereby, the fuel off-gas discharged from FC4 is supplied to FC4.

[0020] 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 moisture from the fuel off-gas discharged from FC4. The water and fuel off-gas stored in the gas-liquid separator 27 are discharged to the outside of the fuel cell system 1 through the discharge pipe 23 when the discharge valve 28 opens. The driving of the tank valve 24, the pressure regulating valve 25, the INJ26a, the LSV26b, and the discharge valve 28 is controlled by the ECU3.

[0021] The ECU3 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU3 is electrically connected to the accelerator opening sensor 6, the display 8, the air compressor 14, the bypass valve 15, the back pressure valve 17, the tank valve 24, the pressure regulating valve 25, the INJ26a, the LSV26b, and the discharge valve 28.

[0022] Based on the detected value of the accelerator opening sensor 6, the driving states of the vehicle auxiliary machines and the FC4 auxiliary machines described above, etc., the ECU 3 calculates the required power generation amount W of the FC4. Further, the ECU 3 calculates the target current value of the FC4 according to the required power generation amount W of the FC4. The ECU 3 controls the flow rates of the oxidant gas and the fuel gas supplied to the FC4 by the air compressor 14, INJ26a, or LSV26b so that the output current value of the FC4 becomes the target current value. The display 8 is provided, for example, on the instrument panel of the vehicle. The ECU 3 executes the reduction control described below by functionally realizing a switching unit, an operation control unit, an integration unit, a reduction control unit, and a notification control unit.

[0023] [Reduction Control] FIG. 2 is a flowchart exemplifying the reduction control executed by the ECU 3. The ECU 3 integrates the number of operations of INJ26a (step S1). The number of operations of INJ26a is the number of times INJ26a opens its valve. It is added to the number of operations integrated at the previous trip, and the number of operations at the current trip is integrated. Step S1 is an example of the process executed by the integration unit.

[0024] Next, the ECU 3 determines whether or not the integrated number of operations is greater than or equal to a threshold value (step S2). The threshold value is set to a number lower by a predetermined number of times than the number of operations required for replacing INJ26a. If the result in step S2 is No, this control ends.

[0025] If the result in step S2 is Yes, the ECU 3 executes reduction control (step S3). The reduction control is a process of reducing the number of operations of INJ26a compared to the case where the result in step S2 is No. Specifically, the reduction control executes an upper limit value change process and a switching value change process. Step S3 is an example of the process executed by the reduction control unit.

[0026] Figure 3 is a timing chart illustrating the process of changing the upper limit. Figure 3 shows the supply pressure P and the on / off state of INJ26a during normal operation and during reduction control. Under normal operation, when the supply pressure P drops to the lower limit pressure value p1, INJ26a is controlled to turn ON and operates. As a result, fuel gas is injected from INJ26a, and the supply pressure P increases. When the supply pressure P rises to the upper limit pressure value p2, INJ26a is controlled to turn OFF and stops operating. As a result, fuel gas injection from INJ26a stops, and the supply pressure P decreases. Pressure value p2 is higher than pressure value p1. Thus, under normal operation, the on / off state of INJ26a is switched with a period t1. The above process is an example of a process executed by the operation control unit.

[0027] In the upper limit change process, the upper limit is changed from pressure value p2 to pressure value p3. Pressure value p3 is higher than pressure value p2. Therefore, during reduction control, as in normal operation, INJ26a is controlled to turn on when the supply pressure P falls to the lower limit pressure value p1. However, during reduction control, unlike in normal operation, INJ26a is controlled to turn off when the supply pressure P rises to the upper limit pressure value p3. For this reason, during reduction control, the on / off switching of INJ26a is performed with a period t2 that is longer than the period t1. As a result, the number of times INJ26a operates is reduced during reduction control compared to normal operation. This improves the lifespan of INJ26a. In addition, although the number of times INJ26a operates is reduced, the INJ26a continues to operate, so the supply pressure P can be accurately maintained between pressure value p1 and pressure value p3.

[0028] In the upper limit change process, the lower limit remains unchanged and is maintained at pressure value p1. This prevents a decrease in FC4 output due to a fuel gas shortage. The difference between pressure value P3 and pressure value P2 may be less than, for example, the difference between pressure value P2 and pressure value P1. This is because if the difference between pressure value P3 and pressure value P2 is excessively large compared to the difference between pressure value P2 and pressure value P1, fuel efficiency will deteriorate.

[0029] Figure 4 is a timing chart illustrating the switching value change process. Figure 3 shows the required power generation W of FC4 and the on / off states of INJ26a and LSV26b during normal operation and reduction control. Figure 3 illustrates the case where the required power generation W of FC4 rises from 0 and then falls again. Under normal conditions, if the required power generation W is less than the switching value w2, INJ26a is driven and LSV26b is stopped. If the required power generation W is equal to or greater than the power value w2, INJ26a is stopped and LSV26b is driven. Thus, under normal conditions, INJ26a is driven for a driving time T2. The above process is an example of the process executed by the switching unit.

[0030] In the switching value change process, the switching value is changed from power value w2 to power value w1. Power value w1 is lower than power value w2. Thus, during reduction control, INJ26a is driven for a drive time T1 which is shorter than the drive time T2. Therefore, the drive time of INJ26a is shortened during reduction control compared to normal operation. This reduces the number of operations of INJ26a and improves the lifespan of INJ26a.

[0031] Next, the ECU3 notifies the driver that the number of INJ26a operations has exceeded a threshold (step S4). The ECU3 may notify the user by displaying this information on the display 8, for example, or by using the MIL (Malfunction Indicator Light) or speaker. This is because the fuel efficiency may worsen due to the execution of the reduction control described above. Step S4 is an example of the processing performed by the notification control unit.

[0032] In the above embodiment, both the upper limit change process and the switching value change process were performed as reduction control, but either the upper limit change process or the switching value change process may be performed alone as reduction control.

[0033] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0034] 1. Fuel cell system 3. ECU (Control Unit, Switching Unit, Operation Control Unit, Accumulation Unit, Reduction Control Unit, Notification Control Unit) 4 fuel cell 26a Injector 26b Linear solenoid valve

Claims

1. Fuel cells and An injector for injecting fuel gas into the fuel cell, A linear solenoid valve that injects fuel gas into the fuel cell and has a fuel gas injection flow rate greater than that of the injector, The system includes a control device for controlling the injector and the linear solenoid valve, The control device is A switching unit that activates the injector when the required power generation of the fuel cell is less than a switching value, and activates the linear solenoid valve when the required power generation is equal to or greater than the switching value. An operation control unit that, when the requested power generation is less than the switching value, activates the injector when the supply pressure of the fuel gas supplied to the fuel cell falls below a lower limit, and stops the operation of the injector when the pressure rises above an upper limit. An accumulator unit for accumulating the number of times the injector operates, and The system includes a reduction control unit that, when the number of operations exceeds a threshold, performs reduction control to reduce the number of operations of the injector compared to when the number of operations is below the threshold, Fuel cell system.

2. The fuel cell system according to claim 1, wherein the reduction control, when the number of operations exceeds the threshold, changes the upper limit to a higher value while maintaining the lower limit than when the number of operations is below the threshold.

3. The fuel cell system according to claim 1, wherein the reduction control changes the switching value to a lower value than when the number of operations is less than the threshold value when the number of operations is greater than or equal to the threshold value.

4. The fuel cell system according to claim 1, wherein the reduction control, when the number of operations exceeds the threshold, changes the upper limit to a higher value while maintaining the lower limit, and changes the switching value to a lower value, compared to when the number of operations is below the threshold.

5. The fuel cell system according to any one of claims 1 to 4, wherein the control device includes a notification control unit that notifies when the number of operations exceeds the threshold.

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