Fuel Cell Systems

Abstract

To provide a technology that can accurately control the supply flow rate of fuel gas even in a small fuel gas flow rate range.SOLUTION: A fuel cell system includes a fuel gas circulation system that includes a linear solenoid valve and an injector arranged in parallel. The injector is capable of supplying fuel gas within a smaller flow rate range than the required flow rate of fuel gas, and the linear solenoid valve is configured to be able to supply a larger flow rate range among the required flow rates. In a flow rate range in which the required flow rate of the fuel gas is less than a first threshold value that is a flow rate that can be supplied by the injector, the injector is used to adjust the supply flow rate of the fuel gas, and in a flow rate range in which the flow rate is equal to or higher than the first threshold, a linear solenoid valve is used to adjust the supply flow rate.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a fuel cell system. [Background technology]

[0002] The amount of fuel gas supplied when the fuel cell starts generating electricity is adjusted according to the power generation status of the fuel cell. For example, during a certain period immediately after the fuel cell starts generating electricity, the pump speed of the circulation pump and the discharge pressure of the fuel gas regulator are adjusted based on the rise rate of the open circuit voltage of the fuel cell during that period, and the amount of fuel gas supplied to the fuel cell is adjusted (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-190336 A Summary of the Invention [Problem to be solved by the invention]

[0004] Linear solenoid valves are sometimes used as fuel gas regulators. Linear solenoid valves generally produce non-choked flow (subsonic flow) in the low flow range. For this reason, when attempting to control the flow rate in the relatively low flow range at the start of power generation in a fuel cell, the accuracy of the flow rate control may decrease.

[0005] The technology disclosed in this specification provides a technology that can precisely control the flow rate of fuel gas in a small flow rate range of fuel gas, for example, at the start of power generation in a fuel cell system. [Means for solving the problem]

[0006] The fuel cell system disclosed in this specification includes an injector and a linear solenoid valve arranged in parallel in a fuel gas circulation system. The injector is capable of supplying fuel gas within a smaller flow rate range of the required flow rate of the fuel gas (hereinafter also simply referred to as the required flow rate), and the linear solenoid valve is configured to supply fuel gas within a larger flow rate range of the required flow rate. When the required flow rate is in a flow rate range below a first threshold that is a flow rate that can be supplied by the injector, the supply flow rate of the fuel gas is adjusted using the injector, and when the required flow rate is in a flow rate range equal to or greater than the first threshold, the supply flow rate of the fuel gas is adjusted using the linear solenoid valve.

[0007] This makes it possible to suppress or avoid a decrease in the flow rate control accuracy of the linear solenoid valve in a small flow rate range where the required flow rate is less than the first threshold, which is the flow rate that can be supplied by the injector, and improves the flow rate controllability in the small flow rate range. On the other hand, in a flow rate range equal to or greater than the first threshold, the linear solenoid valve enables accurate flow rate control. As a result, the controllability of the fuel gas supply flow rate is improved over a wide range of required flow rates.

[0008] In addition, for example, when the residual pressure in the hydrogen tank drops significantly, the first threshold, which is the flow rate that the injector can supply, drops significantly. In this case, the required flow rate is equal to or greater than the first threshold, so that the flow rate of the fuel gas can be controlled by the linear solenoid valve. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing an outline of an example of the configuration of a fuel cell system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an injector characteristic in the fuel system according to the first embodiment. [Diagram 3] FIG. 3 is an explanatory diagram of a linear solenoid valve characteristic in the fuel system of the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a process of a fuel gas flow rate control program in the first embodiment. [Diagram 5] FIG. 4 is a diagram showing an outline of an example of the configuration of a fuel cell system according to a second embodiment. [Figure 6] FIG. 11 is a diagram showing the relationship between the fuel gas supply flow rate and the fuel off-gas circulation flow rate in the ejector in the second embodiment. [Figure 7] FIG. 11 is a diagram showing the relationship between the fuel gas supply flow rate and the fuel off-gas circulation flow rate in the ejector in the third embodiment. [Figure 8] FIG. 11 is a diagram showing an example of a process of a fuel gas flow rate control program in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In one embodiment of the fuel cell system of the present disclosure, the injector may be configured to supply fuel gas in a choked flow in at least a portion of the non-choked flow region of the linear solenoid valve. In this way, the injector can supply fuel gas in a choked flow in the non-choked flow region of the linear solenoid valve to adjust the flow rate. This makes it possible to suppress or avoid a decrease in flow rate controllability due to the non-choked flow of the linear solenoid valve.

[0011] In one embodiment of the fuel cell system of the present disclosure, an ejector may be further provided to recirculate exhaust gas from the fuel gas outlet to the fuel gas inlet of the fuel cell, thereby increasing the exhaust gas circulation flow rate even in the low flow rate range where the injector operates.

[0012] In an embodiment of the fuel cell system of the present disclosure that includes an ejector, the fuel gas supply flow rate may be adjusted by the injector when the required flow rate is in a range below a first threshold, the fuel gas supply flow rate may be adjusted by the injector and the linear solenoid valve when the required flow rate is in a second flow rate range that is equal to or greater than the first threshold and less than a second threshold that exceeds the first threshold, and the fuel gas supply flow rate may be adjusted by the linear solenoid valve when the required flow rate is in a third flow rate range that is equal to or greater than the second threshold. In this way, the controllability of the fuel gas supply flow rate can be improved according to the required flow rate, the fuel gas supply capacity of the injector, and the fuel gas supply capacity of the linear solenoid valve, and the exhaust gas circulation flow rate can be increased over a wide flow rate range.

[0013] In this specification, the terms "above or above," "exceed," "below or below," and "below" in relation to thresholds such as the first threshold and the second threshold are set in relation to numerical values, and depending on the numerical value of the set threshold, they are expressed as "above or above" or "exceed," and similarly as "below or below" or "below." Thus, "above or above" and "exceed" can mutually include the meaning of the other, and the same applies to "below or below" and "below."

[0014] Hereinafter, the supply flow rate control of hydrogen as fuel gas in the fuel cell system disclosed in this specification will be described with reference to the drawings as appropriate.

[0015] The fuel cell system described below includes a stack in which many fuel cells are stacked in series, a hydrogen circulation system, and a control device. The fuel cell system also includes an air supply system that supplies air, which is an oxidant gas, and a cooling system consisting of a cooling water pump, a cooling water flow path, and the like. Fuel cell systems are well known in the art, and may be systems that include various fuel cells, including polymer electrolyte fuel cells (PEFCs). The use of the fuel cell system is not particularly limited. For example, the fuel cell system may be a mobile fuel cell system that is mounted on a mobile body such as a vehicle or a ship, or a stationary fuel cell system that is used in stationary power generation facilities.

[0016] (First embodiment) An outline of the configuration of a fuel cell system 2 according to a first embodiment disclosed in this specification is shown in Fig. 1. The fuel cell system 2 includes a fuel cell 4, a hydrogen circulation system 6 in which hydrogen as a fuel gas circulates, an air supply system (not shown) that supplies air as an oxidizing gas, and a control device 10. In addition, the fuel cell system 2 includes a cooling water circulation system for cooling the fuel cell 4, although this is not shown.

[0017] The hydrogen circulation system 6 includes a supply flow path 20 that supplies hydrogen, which is a fuel gas, to the fuel gas inlet 4a of the fuel cell 4, and a discharge flow path 22 that discharges fuel off-gas (hereinafter simply referred to as off-gas), which is an exhaust gas discharged from the fuel gas outlet 4b of the fuel cell 4. The supply flow path 20 includes a hydrogen tank 30, a pressure sensor 32, an injector 40, and a linear solenoid valve 50.

[0018] The tank 30 may be any hydrogen storage device, and may take various known forms, such as a compressed hydrogen cylinder, a liquid hydrogen tank, a hydrogen storage alloy, etc. The pressure sensor 32 is located downstream of the tank 30 in the supply flow path 20, and detects the pressure of the fuel gas from the tank 30.

[0019] The injector 40 and the linear solenoid valve 50 are arranged in parallel so that fuel gas from the tank 30 is supplied to only one of them. The injector 40 and the linear solenoid valve 50 both adjust the flow rate of hydrogen supplied to the fuel gas inlet 4a of the fuel cell 4. Valves for supplying or stopping hydrogen to the injector 40 and the linear solenoid valve 50 may be appropriately provided upstream of these.

[0020] The injector 40 is an on-off valve that can adjust the supply flow rate and pressure of the fuel gas from the primary side (tank 30) to the secondary side (fuel gas inlet 4a), for example, by driving the valve body at a predetermined drive cycle using an electromagnetic driving force or the like to move it away from the valve seat.

[0021] 2(a), the injector 40 can be used in two basic positions, "open" and "closed," by turning on and off a current supplied to a coil provided in the injector 40. By opening and closing the injector 40, the flow rate of the fuel gas supplied from the injector 40 to the fuel gas inlet 4a can be changed in a stepped manner. Therefore, by controlling the injector 40, the supply of fuel gas to the fuel gas inlet 4a can be cut off and the fuel gas can be intermittently supplied to the fuel gas inlet 4a, thereby controlling the flow rate of the fuel gas supplied to the fuel gas inlet 4a.

[0022] As shown in FIG. 2(b), the injector 40 has a specific critical pressure ratio X at which the flow switches between non-choked flow (subsonic flow) and choked flow in the relationship between the pressure ratio (primary pressure / secondary pressure) and the supply flow rate. At pressure ratios below the critical pressure ratio X, the supply flow rate depends on the pressure ratio, and at pressure ratios above the critical pressure ratio X, the supply flow rate depends on the primary pressure. For example, as shown in FIG. 2(b), the injector 40 can supply fuel gas with high accuracy in the flow rate range a1 to a2 by being used in a choked flow region A of a predetermined pressure ratio range above the critical pressure ratio X. The choked flow region A is also a region set as being suitable for use by the fuel cell system 2.

[0023] 3(a), the linear solenoid valve 50 controls the opening from the primary side (tank 30) to the secondary side (fuel gas inlet 4a) to any opening between the maximum opening and the closed valve by a plunger driven by a solenoid, thereby arbitrarily controlling the fuel gas supply flow rate. The structure of such linear solenoid valve 50 is not particularly limited, and the structure of a known linear solenoid valve can be adopted.

[0024] 3(b), the linear solenoid valve 50, like the injector 40, also has an inherent critical pressure ratio Y, and switches between non-choked flow and choked flow around the critical pressure ratio Y. The linear solenoid valve 50 can supply fuel gas with high precision in a flow rate range of b1 or more by being used in a choked flow region B with a stable choked flow pressure ratio that exceeds this critical pressure ratio. On the other hand, in the non-choked flow region C1, which is a smaller flow rate region within the non-choked flow region C, the linear solenoid valve 50 may have difficulty in controlling the flow rate in proportion to the opening, and the precision of the supply flow rate may decrease.

[0025] Here, the injector 40 and the linear solenoid valve 50 are configured such that the injector 40 can supply fuel gas in a smaller flow rate range within the required flow rate range of the fuel gas, and the linear solenoid valve 50 can supply fuel gas in a larger flow rate range within the required flow rate range. For example, the choked flow region A of the injector 40 is set to be included in a non-choked flow region C, which is a pressure ratio smaller than the inherent critical pressure ratio of the linear solenoid valve 50. Also, for example, the inherent critical pressure ratio X of the injector 40 is set to be smaller than the inherent critical pressure ratio Y of the linear solenoid valve 50 and closer to a pressure ratio of 1. More specifically, the non-choked flow region C1 of the linear solenoid valve 50 is set to be substantially covered by the choked flow region A of the injector 40.

[0026] Also, for example, the upper limit a2 of the supply flow rate in the choked flow region A of the injector 40 roughly coincides with the lower limit b1 of the flow rate range in the choked flow region B of the linear solenoid valve 50.

[0027] The injector 40 and linear solenoid valve 50 thus configured are both connected to a control device 10. In the injector 40, the drive of the valve body is controlled by an output signal from the control device 10, and in the linear solenoid valve 50, the drive of the solenoid, plunger, etc. is controlled by an output signal from the control device 10.

[0028] The exhaust passage 22 is configured to be able to exhaust the off-gas exhausted from the fuel gas outlet 4b. An exhaust valve (not shown) is provided in the exhaust passage 22, and the off-gas is exhausted by opening and closing the exhaust valve.

[0029] The control device 10 is configured as a computer equipped with a processor and memories such as RAM and ROM. In accordance with a program stored in the ROM or the like, the control device 10 controls the operation of each part of the fuel cell system 2. The control device 10 is equipped with an executable fuel gas supply flow rate control program that outputs a control signal to the injector 40 or the linear solenoid valve 50 to control the supply flow rate of the fuel gas.

[0030] The control device 10 is also connected to a pressure sensor 32, an injector 40, a linear solenoid valve 50, etc., and acquires pressure signals and the like from these devices and stores them in a memory as appropriate. The control device 10 is also connected to an input unit of a power supply target device (external device) to which the fuel cell system 2 is connected, and acquires an input amount from the input unit.

[0031] Next, the process and operation of controlling the fuel gas supply flow rate in the fuel cell system 2 will be described with reference to Fig. 4. When the processor of the control device 10 detects an input from an input unit of an external device, it executes a process defined in a fuel gas supply flow rate control program and outputs signals for controlling the injector 40 and / or the linear solenoid valve 50, etc., to cause them to perform predetermined operations. Note that in the following description, it is assumed that the remaining amount of fuel gas in the tank 30 of the fuel cell system 2 is equal to or greater than a certain amount, and that the lower limit pressure ratio of the choke flow region A of the injector 40 is ensured.

[0032] First, the processor of the control device 10 calculates the amount of output required of the fuel cell 4 based on the input amount acquired from the input unit of the external device (step S10). For example, if the external device is a vehicle, the amount of output is calculated based on the accelerator opening by the driver, the vehicle conditions, etc.

[0033] Furthermore, the processor calculates the required flow rate FR to be supplied to the fuel cell 4 in order to obtain this output amount, based on, for example, the power generation performance characteristics inherent to the fuel cell 4, the temperature of the fuel cell 4, and the like (step S20).

[0034] The processor also calculates the fuel gas supply capacity of the injector 40 that can be provided at this time, i.e., the supply flow rate F1 that the injector 40 can supply, based on the characteristics of the injector 40, based on the primary pressure (pressure) from the pressure sensor 32, etc. (step S30). The supply flow rate F1 is the maximum fuel gas supply flow rate calculated based on the remaining amount of fuel gas in the tank 30, etc. in the fuel cell system 2, and the temperature. The supply flow rate F1 corresponds to, for example, the supply flow rate a2 achieved by the choke flow region A in FIG. 2(b). Here, the supply flow rate F1 is an example of the first threshold value disclosed in this specification.

[0035] The processor further compares the required flow rate FR with the supply flow rate F1, and determines whether the required flow rate FR is smaller than the supply flow rate F1 (step S40).

[0036] When the required flow rate FR is smaller than the supply flow rate F1, the processor adjusts the supply flow rate of the fuel gas by the injector 40 without using the linear solenoid valve 50, and outputs a control signal for that purpose to the injector 40 (step S50). At this time, it is also possible to output necessary control signals to the linear solenoid valve 50, an on-off valve, etc., as appropriate, at the same time as the above output.

[0037] At this required flow rate FR, the injector 40 is in the choked flow region A, so that even if the required flow rate FR is a small flow rate, the supply flow rate of the fuel gas is accurately adjusted by the injector 40.

[0038] On the other hand, when the required flow rate FR is equal to or greater than the supply flow rate F1, the processor adjusts the supply flow rate of fuel gas by the linear solenoid valve 50 without using the injector 40, and outputs a control signal for that purpose to the linear solenoid valve 50. At this time, necessary control signals may be output to the injector 40, the on-off valve, etc., as appropriate, simultaneously with the output.

[0039] At this required flow rate FR, the linear solenoid valve 50 is in the choke flow region B, so the supply flow rate is adjusted with high precision.

[0040] The processor then ends this process. The program process is started at the necessary timing, and the supply flow rate of the fuel gas is controlled by the injector 40 or the linear solenoid valve 50 according to the output required for the fuel cell 4, etc.

[0041] As described above, the primary pressure fluctuates depending on the amount of fuel gas remaining in the tank 30 in the fuel cell system 2, etc. As a result, the supply flow rate F1 of the injector 40 may also fluctuate. In the fuel cell system 2, the required flow rate FR and the supply flow rate F1 required for the fuel cell 4 are calculated, and an optimal flow rate regulator for regulating the supply flow rate of the fuel gas in the fuel cell system 2 can be selected. As a result, the controllability of the flow rate of the fuel gas to the fuel cell 4 can be improved.

[0042] In the above description, the case where the remaining amount of fuel gas in the tank 30 is equal to or greater than a certain amount has been described, but the above program process is also effective when the remaining amount of fuel gas in the tank 30 decreases and the primary pressure drops too much. In such a case, the pressure ratio falls below the pressure ratio of the choked flow region A of the injector 40, entering a non-choked region, and the supply flow rate F1 also decreases. When the processor executes the above process, the required flow rate FR becomes equal to or greater than the supply flow rate F1 (step S40), and the processor controls the linear solenoid valve 50 to be used (step S50). This ensures the supply of fuel gas to the fuel cell 4.

[0043] Second embodiment An outline of the configuration of a fuel cell system 102 of the second embodiment is shown in Figure 5. In the following description, for the fuel cell system 102, the same elements as those in the fuel cell system 2 of the first embodiment are given the same reference numbers and the description thereof will be omitted.

[0044] The fuel cell system 102 includes a fuel gas circulation flow path 60 in place of the fuel gas exhaust flow path 22. The circulation flow path 60 is configured to return the off-gas to the fuel gas inlet 4a. If necessary, the circulation flow path 60 includes a circulation pump driven by a motor or the like for compressing the off-gas to an appropriate gas pressure and returning it to the supply flow path 20. In addition, an exhaust flow path 62 for exhausting the gas to the outside of the fuel cell system 2 via a diluter is branched off from the circulation flow path 60.

[0045] 5, the fuel cell system 102 includes an ejector 70. The ejector 70 is provided at a connection between the supply flow passage 20 and the circulation flow passage 60 on the downstream side of the injector 40.

[0046] Fig. 6 shows the relationship between the fuel gas supply flow rate and the fuel off-gas circulation flow rate in the ejector 70. As shown in Fig. 6(a), in the ejector 70, off-gas is sucked from the circulation flow path 60 by the fuel gas flowing into the ejector 70 from the tank 30 via the injector 40 or the linear solenoid valve 50. Also, as shown in Fig. 6(b), when the injector 40 or the linear solenoid valve 50 is used, if the pressure difference (P2-P3) between the secondary pressure P2 and the suction pressure P3 of the circulation flow path 60 is constant, the greater the supply flow rate, the greater the circulation flow rate of the off-gas.

[0047] With this configuration, for example, the following operations become possible when executing the process defined in the fuel gas flow rate control program described in the first embodiment.

[0048] For example, when it is determined in step S40 of the flow rate control program in the first embodiment that the required flow rate FR is smaller than the supply flow rate F1, fuel gas is supplied in the choked flow region A of the injector 40 (step S50). That is, the injector 40 can generate a sufficient differential pressure during the choked flow to effectively increase the circulation flow rate of the off-gas. Conventionally, when the flow rate of fuel gas is adjusted by a linear solenoid valve, the differential pressure is small at a fuel gas supply flow rate that results in a non-choked flow, and the circulation flow rate of the off-gas cannot be increased. However, according to the second embodiment, even in a small flow rate region (small output region) where the required flow rate FR is smaller than the supply flow rate F1, the supply flow rate is adjusted by the injector 40, and the circulation flow rate can be increased at the same time.

[0049] As described above, even in the small flow rate region corresponding to the non-choked flow region B of the linear solenoid valve 50, by adjusting the supply flow rate by the injector 40, the circulating flow rate of the off-gas can be increased.

[0050] (Third embodiment) The third embodiment relates to the use of other characteristics of the injector 40 and the linear solenoid valve 50 in the fuel cell system 102 described in the second embodiment. The characteristics and the process and operation of controlling the supply flow rate of fuel gas based on the characteristics will be described with reference to Figures 7 and 8. As with the second embodiment, the description of the same elements as in the first embodiment will be simplified or omitted.

[0051] Fig. 7 shows the relationship between the supply flow rate of fuel gas and the circulation flow rate of off-gas in the ejector of this embodiment. As shown in Fig. 7, in the choke flow region A of the injector 40, which is less than the supply flow rate F1 corresponding to the maximum supply flow rate, the circulation flow rate of off-gas by the injector 40 is configured to considerably exceed the circulation flow rate of off-gas by the linear solenoid valve 50.

[0052] On the other hand, in a region equal to or greater than the supply flow rate F1 and less than the predetermined supply flow rate T within the flow rate range of the supply amount handled by the linear solenoid valve 50, the circulation flow rate by the linear solenoid valve 50 gradually increases. Furthermore, in a flow rate range equal to or greater than the predetermined supply flow rate T, the circulation flow rate by the linear solenoid valve 50 is configured to exceed the circulation flow rate by the injector 40. This is because in the small flow rate range, the linear solenoid valve 50 is less likely to generate a large differential pressure than the injector 40, and therefore the circulation flow rate may tend not to increase easily.

[0053] Here, a predetermined fuel gas supply flow rate T (hereinafter also referred to as a circulation flow rate threshold T) at which the circulation flow rate by the linear solenoid valve 50 exceeds the circulation flow rate by the injector 40 is determined based on, for example, the fuel gas supply flow rate F1 calculated by the processor based on the pressure and the like acquired from the pressure sensor 32 and the like, the fuel gas supply flow rate F2 by the linear solenoid valve 50 similarly calculated based on the pressure and the like, and the characteristics of the ejector 70. Such circulation flow rate threshold T is stored in advance in the ROM together with this flow rate control program as a table including several circulation flow rate thresholds T associated with the supply flow rates F1, F2, and the like. The circulation flow rate threshold T is read into the RAM together with the program prior to execution of the program.

[0054] The circulation flow rate threshold T is an example of a second threshold disclosed in this specification, the fuel gas flow rate range less than the supply flow rate F1 is a first flow rate range in this specification, the flow rate range equal to or greater than the supply flow rate F1 and less than the circulation flow rate threshold T is an example of a second flow rate range in this specification, and the flow rate range equal to or greater than the circulation flow rate threshold T is an example of a third flow rate range in this specification.

[0055] In the fuel cell system 102, when the injector 40, the linear solenoid valve 50, and the ejector 70 have such a configuration, in the flow rate range between the supply flow rate F1 and the circulation flow rate threshold T, it may be advantageous to combine the supply of fuel gas by the injector 40 with the supply of fuel gas by the linear solenoid valve 50 in order to increase the circulation flow rate.

[0056] For example, the required flow rate FR can be met by alternately using the injector 40 and the linear solenoid valve 50 based on the respective characteristics of the injector 40 and the linear solenoid valve 50. More specifically, examples of such modes include a mode in which the injector 40 and the linear solenoid valve 50 are operated at the same level, a mode in which the injector 40 is operated primarily while the linear solenoid valve 50 is operated to make up for any shortage, and a mode in which the linear solenoid valve 50 is operated primarily while the injector 40 is operated to make up for any shortage. These modes of use may be used alone or in combination depending on the level of increase in the circulation flow rate, etc.

[0057] Next, the process and operation of controlling the supply flow rate of fuel gas in the fuel cell system 102 will be described with reference to Fig. 8. Note that steps S110 to S140 executed by the processor of the control device 10 are similar to steps S10 to S40 in the first embodiment, and therefore description thereof will be omitted.

[0058] When the required flow rate FR is smaller than the supply flow rate F1, the processor determines that the supply flow rate of fuel gas will be adjusted by the injector 40 without using the linear solenoid valve 50, and outputs a control signal for this purpose to the injector 40 (step S150). At this required flow rate FR, the supply flow rate F1 of the injector 40 is in the choke flow region A, so that the injector 40 accurately adjusts the supply flow rate F1 of fuel gas, and at the same time, the ejector 70 sucks in off-gas from the circulation flow path 60 when the injector 40 is open, and the fuel off-gas is also supplied to the fuel cell 4.

[0059] On the other hand, when the required flow rate FR is equal to or greater than the supply flow rate F1, the processor calculates the fuel gas supply capacity that the linear solenoid valve 50 can provide, i.e., the supply flow rate F2, based on the primary pressure (pressure) from the pressure sensor 32 and the characteristics of the linear solenoid valve 50 (step S160).

[0060] Next, the processor obtains the circulation flow rate threshold T based on the supply flow rates F1, F2 and the table of the circulation flow rate threshold T read into the RAM, and determines whether the requested flow rate FR is less than the circulation flow rate threshold T (step S170).

[0061] When the required flow rate FR is less than the circulation flow rate threshold T, the processor alternately outputs control signals to the injector 40 and the linear solenoid valve 50 so that the injector 40 and the linear solenoid valve 50 satisfy the required flow rate FR and ensure or increase the circulation flow rate (step S180). In this flow rate range, the effect of increasing the circulation flow rate by the linear solenoid valve 50 is small, but the circulation flow rate can be ensured or increased by using the injector 40 in combination.

[0062] On the other hand, when the required flow rate FR is equal to or greater than the circulation flow rate threshold T, the processor outputs a control signal to the linear solenoid valve 50 to cause the linear solenoid valve 50 to satisfy the required flow rate FR and increase the circulation flow rate (step S190). In this flow rate range, the increase in the circulation flow rate by the linear solenoid valve 50 is sufficient, so the circulation flow rate can be secured or increased by the linear solenoid valve 50 alone.

[0063] The program flow is executed at the required timing, and the supply flow rate of fuel gas and the circulation flow rate of off-gas are controlled by the injector 40 and / or the linear solenoid valve 50 and the ejector 70 according to the output required for the fuel cell 4, etc.

[0064] As described above, according to the fuel cell system 102, when the required flow rate FR is less than the supply flow rate F1 of the injector 40, the injector 40 accurately supplies fuel gas and increases the circulation flow rate, and when the required flow rate FR is equal to or greater than the supply flow rate F1 and less than the circulation flow rate threshold T, the injector 40 and the linear solenoid valve 50 are alternately used to accurately supply fuel gas and increase the circulation flow rate. When the required flow rate FR is equal to or greater than the circulation flow rate threshold T, the linear solenoid valve 50 supplies fuel gas and increases the circulation flow rate. This makes it possible to accurately control the required flow rate FR over a wide flow rate range, and also to increase and control the circulation flow rate of the off-gas over a wide flow rate range.

[0065] In the above first to third embodiments, the choke flow region A of the injector 40 is set as a region that can be suitably used by the fuel cell system 2, and is a predetermined region within a predetermined pressure ratio range equal to or greater than the critical pressure ratio X of the injector 40. However, above the critical pressure ratio X, the choke flow region A is appropriately set within the capacity range of the injector 40 so as to match the characteristics of the fuel cell system 2, 102.

[0066] In the above first to third embodiments, the choked flow region A of the injector 40 is set so as to substantially coincide with the non-choked flow region C1 having a smaller pressure ratio within the non-choked flow region C of the linear solenoid valve 50 that is less than the critical pressure ratio Y, but this is not limited to this. The choked flow region A can be set so as to coincide with an appropriate region of the whole or part of the non-choked flow region depending on the characteristics of the injector 40 and the linear solenoid valve 50, etc.

[0067] Specific examples of the technology disclosed in this specification have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above, such as a control method for a fuel cell. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. The technology exemplified in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of the objectives itself has technical usefulness. [Explanation of symbols]

[0068] 2, 102 Fuel Cell System 4 fuel cell 6 Hydrogen Circulation System 10 Control device 20 Supply Channel 22 Exhaust flow path 30 Hydrogen Tank 40 Injector 50 Linear solenoid valve 60 Circulation flow path 62 Exhaust flow path 70 Ejector

Claims

1. 1. A fuel cell system comprising: A fuel gas circulation system including a linear solenoid valve and an injector arranged in parallel, the injector is configured to supply the fuel gas within a smaller flow rate range of the required flow rate of the fuel gas, and the linear solenoid valve is configured to supply the fuel gas within a larger flow rate range of the required flow rate, a supply flow rate of the fuel gas is adjusted using the injector when the required flow rate is in a flow rate range less than a first threshold value that is a flow rate that can be supplied by the injector, and a supply flow rate of the fuel gas is adjusted using the linear solenoid valve when the required flow rate is in a flow rate range equal to or greater than the first threshold value; A fuel cell system, wherein the injector is configured to be able to supply fuel gas in a choked flow in at least a portion of a non-choked flow region of the linear solenoid valve.

2. 2. The fuel cell system according to claim 1, further comprising an ejector that recirculates exhaust gas from the fuel gas outlet of the fuel cell to the fuel gas inlet of the fuel cell.

3. adjusting a supply flow rate of the fuel gas using the injector when the required flow rate is in a first flow rate range that is less than the first threshold value; when the required flow rate is in a second flow rate range of a flow rate equal to or greater than the first threshold value, exceeding the first threshold value and less than a second threshold value, adjusting a supply flow rate of the fuel gas using the injector and the linear solenoid valve; 3. The fuel cell system according to claim 2, wherein when the required flow rate is in a third flow rate range that is equal to or greater than the second threshold value, the linear solenoid valve is used to adjust the supply flow rate of the fuel gas.

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