fuel cell system

Abstract

To learn the dynamic characteristics of a solenoid valve used for a fuel cell system.SOLUTION: A fuel cell system has: a fuel cell; a hydrogen gas supply path that supplies a hydrogen gas to the fuel cell; a solenoid valve that changes the opening of the hydrogen gas supply path; a pressure sensor that detects a pressure in a downstream side supply path from the solenoid valve to the fuel cell, of the hydrogen gas supply path; and a control circuit that controls the solenoid valve. The control circuit executes the following steps of: detecting an application current of the solenoid valve and the pressure at a plurality of points while changing the application current of the solenoid valve at a first sweep speed, and storing the detected application currents and pressures; and detecting the application current and the pressure at a plurality of points while changing the application current at a second sweep speed different from the first sweep speed, and storing the detected application currents and pressures.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a solenoid valve that controls the hydraulic pressure of a vehicle's brake fluid. A control circuit that controls the solenoid valve stores an initial drive amount as a current value for driving the solenoid valve. The control circuit stores the initial drive amount according to the differential pressure between the upstream and downstream sides of the solenoid valve. When operating the solenoid valve, the control circuit first passes a current of the initial drive amount through the solenoid valve.

[0003] Individual solenoid valve characteristics vary. Furthermore, the characteristics of a solenoid valve change due to factors such as temperature and aging. In Patent Document 1, a control circuit corrects the initial drive amount to account for variations in the solenoid valve characteristics. Specifically, the control circuit first controls the brake pressure to a target pressure (i.e., a constant value). While the brake pressure is controlled to the target pressure, the current flowing through the solenoid valve also remains approximately constant. In this state, the control circuit measures the brake pressure differential and the current flowing through the solenoid valve. Then, the control circuit corrects the stored initial drive amount based on the measured current. By correcting the initial drive amount in this way according to the characteristics of the solenoid valve, it is possible to control the brake pressure more accurately. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-091577 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 detects the brake pressure differential and current while controlling the brake pressure and the current flowing through the solenoid valve to be approximately constant. However, the characteristics of the solenoid valve differ in a dynamic state where the current flowing through the solenoid valve is changing from a static state where the current flowing through the solenoid valve is constant. The technology of Patent Document 1 cannot accurately learn the characteristics of the solenoid valve when the current flowing through the solenoid valve is changing (hereinafter sometimes referred to as dynamic characteristics). This specification proposes technology that can learn the dynamic characteristics of a solenoid valve used in a fuel cell system. [Means for solving the problem]

[0006] The fuel cell system disclosed in this specification includes a fuel cell, a hydrogen gas supply path that supplies hydrogen gas to the fuel cell, a solenoid valve that changes the opening of the hydrogen gas supply path, a pressure sensor that detects the pressure in a downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell, and a control circuit that controls the solenoid valve, wherein the control circuit executes the steps of: detecting and storing the current and the pressure at multiple points while changing the current flowing through the solenoid valve at a first sweep speed; and detecting and storing the current and the pressure at multiple points while changing the current flowing through the solenoid valve at a second sweep speed that is different from the first sweep speed.

[0007] The first sweep speed and the second sweep speed may be positive values ​​(i.e., values ​​that increase the energizing current) or negative values ​​(i.e., values ​​that decrease the energizing current). Also, the first sweep speed may be positive and the second sweep speed may be negative. In this case, the absolute value of the first sweep speed and the absolute value of the second sweep speed may be the same.

[0008] In addition, the control circuit may first perform either the "step of detecting the energizing current and the pressure at a plurality of points while changing the energizing current of the solenoid valve at a first sweep speed" or the "step of detecting the energizing current and the pressure at a plurality of points while changing the energizing current at a second sweep speed different from the first sweep speed."

[0009] In this fuel cell system, the control circuit learns the dynamic characteristics of the solenoid valve at the first sweep speed by detecting the current and pressure at multiple points while changing the current flowing through the solenoid valve at a first sweep speed. Also, the control circuit learns the dynamic characteristics of the solenoid valve at the second sweep speed by detecting the current and pressure at multiple points while changing the current flowing through the solenoid valve at a second sweep speed different from the first sweep speed. In this way, this fuel cell system can learn the dynamic characteristics of the solenoid valve for each sweep speed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram of a fuel cell system. [Figure 2] Graph showing the dynamic characteristics of LSV for each sweep speed. [Figure 3] 10 is a flowchart showing a learning process. [Figure 4] Graph showing measurements of dynamic characteristics when increasing LSV current. [Figure 5] Graph showing measurements of dynamic characteristics during reduction of LSV current. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the fuel cell system according to the example disclosed herein, in the step of changing the energizing current at the first sweep speed, the control circuit may increase the energizing current at the first sweep speed from a state in which the solenoid valve is closed. Also, in the step of changing the energizing current at the second sweep speed, the control circuit may increase the energizing current at the second sweep speed from a state in which the solenoid valve is closed.

[0012] According to this configuration, the dynamic characteristics of the solenoid valve when the energizing current is increased can be learned at different sweep speeds.

[0013] In the fuel cell system according to the example disclosed herein, the control circuit may decrease the energizing current at the first sweep speed from a state in which the solenoid valve is open in the step of changing the energizing current at the first sweep speed. Also, the control circuit may decrease the energizing current at the second sweep speed from a state in which the solenoid valve is open in the step of changing the energizing current at the second sweep speed.

[0014] This configuration allows learning the dynamic characteristics of the solenoid valve when the energizing current is reduced at different sweep speeds.

[0015] In the fuel cell system according to the present specification, the first sweep rate may be a positive value that increases the energizing current, and the second sweep rate may be a negative value that decreases the energizing current. In the step of changing the energizing current at the first sweep rate, the control circuit may increase the energizing current at the first sweep rate from a state in which the solenoid valve is closed. In the step of changing the energizing current at the second sweep rate, the control circuit may decrease the energizing current at the second sweep rate from a state in which the solenoid valve is open.

[0016] According to this configuration, it is possible to learn the dynamic characteristics of the solenoid valve when the energizing current is increased and the dynamic characteristics of the solenoid valve when the energizing current is decreased.

[0017] 1 is mounted on an electric vehicle. The electric vehicle has a motor 76. The motor 76 operates using the electric power generated by the fuel cell system 10 to rotate the drive wheels of the vehicle.

[0018] The fuel cell system 10 has a fuel cell stack 20, an oxygen gas supply device 30, and a hydrogen gas supply device 40. The fuel cell stack 20 is a stack of multiple fuel cells. The oxygen gas supply device 30 has an oxygen gas supply path 32 arranged to pass through the fuel cell stack 20. Oxygen gas is supplied to the fuel cell stack 20 through the oxygen gas supply path 32. The hydrogen gas supply device 40 has a hydrogen gas supply path 42 arranged to pass through the fuel cell stack 20. Hydrogen gas is supplied to the fuel cell stack 20 through the hydrogen gas supply path 42. Within the fuel cell stack 20, oxygen gas supplied through the oxygen gas supply path 32 and hydrogen gas supplied through the hydrogen gas supply path 42 react with each other. As a result, electricity is generated in the fuel cell stack 20.

[0019] The fuel cell stack 20 is electrically connected to a battery 70, a motor drive circuit 72, and an auxiliary drive circuit 74. When the output current of the fuel cell stack 20 is supplied to the battery 70, the battery 70 is charged. The motor drive circuit 72 operates by receiving power from the fuel cell stack 20 or the battery 70. The motor drive circuit 72 converts the DC voltage supplied from the fuel cell stack 20 or the battery 70 into an AC voltage and supplies it to the motor 76, thereby operating the motor 76. The auxiliary drive circuit 74 operates by receiving power from the fuel cell stack 20 or the battery 70. The auxiliary drive circuit 74 converts the DC voltage supplied from the fuel cell stack 20 or the battery 70 into a lower voltage and supplies it to the auxiliary device 78, thereby operating the auxiliary device 78.

[0020] The hydrogen gas supply device 40 includes a hydrogen gas supply source 44, a linear solenoid valve 46 (hereinafter referred to as LSV (Linear Solenoid Valve) 46), a control circuit 48, an ejector 50, a gas-liquid separator 52, a pressure sensor 54, and an exhaust valve 56.

[0021] The hydrogen gas supply source 44 is connected to the upstream end of the hydrogen gas supply path 42. The hydrogen gas supply source 44 is configured by, for example, a hydrogen gas tank, etc. The hydrogen gas supply source 44 supplies high-pressure hydrogen gas to the hydrogen gas supply path 42.

[0022] The LSV 46 and the ejector 50 are installed in the hydrogen gas supply channel 42. The ejector 50 is installed in the hydrogen gas supply channel 42 downstream of the LSV 46. Furthermore, downstream of the ejector 50, the hydrogen gas supply channel 42 passes through the inside of the fuel cell stack 20. Hydrogen gas supplied from the hydrogen gas supply source 44 passes through the LSV 46, the ejector 50, and the fuel cell stack 20 in that order. In the following, the portion of the hydrogen gas supply channel 42 upstream of the LSV 46 is referred to as supply channel 42a. Furthermore, in the following, the portion of the hydrogen gas supply channel 42 between the LSV 46 and the ejector 50 is referred to as supply channel 42b. Furthermore, in the following, the portion of the hydrogen gas supply channel 42 between the ejector 50 and the fuel cell stack 20 is referred to as supply channel 42c. Furthermore, in the following, the portion of the hydrogen gas supply channel 42 downstream of the fuel cell stack 20 is referred to as supply channel 42d.

[0023] The LSV 46 is a valve that opens and closes the hydrogen gas supply channel 42. A control circuit 48 is electrically connected to the LSV 46. The control circuit 48 controls the current (hereinafter referred to as the LSV current I) that flows through the LSV 46. The opening degree of the LSV 46 changes depending on the LSV current I. When the LSV current I is not flowing, the LSV 46 is closed. The higher the LSV current I, the greater the opening degree of the LSV 46. When the LSV 46 is open, hydrogen gas flows from the supply channel 42a through the LSV 46 to the supply channel 42b.

[0024] An off-gas circulation path 58 is connected to the ejector 50. Off-gas, which is hydrogen gas after passing through the fuel cell stack 20, flows through the off-gas circulation path 58. The off-gas is supplied from the off-gas circulation path 58 to the ejector 50. The ejector 50 adds the off-gas to the hydrogen gas supplied from the supply path 42b and injects the added hydrogen gas into the supply path 42c.

[0025] The hydrogen gas injected from the ejector 50 into the supply path 42c flows into the fuel cell stack 20. The hydrogen gas reacts with oxygen gas inside the fuel cell stack 20. The hydrogen gas that has passed through the fuel cell stack 20 (i.e., off-gas) flows from the fuel cell stack 20 to the supply path 42d.

[0026] The gas-liquid separator 52 is connected to the downstream end of the supply path 42d. An off-gas circulation path 58 and a discharge path 60 are also connected to the gas-liquid separator 52. The gas-liquid separator 52 removes moisture from the off-gas supplied from the supply path 42d. The gas-liquid separator 52 discharges the moisture and excess off-gas to the outside of the fuel cell system 10 via the discharge path 60. The gas-liquid separator 52 also supplies the off-gas from which moisture has been removed to the off-gas circulation path 58. Therefore, as described above, the off-gas is supplied from the off-gas circulation path 58 to the ejector 50.

[0027] A branch path 62 is connected to the supply path 42c. A pressure sensor 54 and an exhaust valve 56 are provided in the branch path 62. When the exhaust valve 56 is open, the branch path 62 is connected to the outside (i.e., the atmosphere). When the exhaust valve 56 is closed, the pressure of hydrogen gas in the branch path 62 is equal to the pressure of hydrogen gas in the supply path 42c. The pressure sensor 54 detects the pressure in the branch path 62. When the exhaust valve 56 is closed, the pressure detected by the pressure sensor 54 is equal to the pressure in the supply path 42c.

[0028] When power generation is performed in the fuel cell system 10, the control circuit 48 opens the LSV 46 to a predetermined opening degree. As a result, hydrogen gas is supplied to the fuel cell stack 20 through the hydrogen gas supply path 42. Oxygen gas is also supplied to the fuel cell stack 20 through the oxygen gas supply path 32. The hydrogen gas and oxygen gas react inside the fuel cell stack 20 to generate electric power. The electric power generated in the fuel cell stack 20 is supplied to the battery 70, the motor drive circuit 72, or the accessory drive circuit 74 as needed.

[0029] FIG. 2 shows the dynamic characteristics of the LSV 46. The horizontal axis of FIG. 2 represents the LSV current I, and the vertical axis of FIG. 2 represents the pressure P in the supply path 42c. Note that the pressure P is equal to the pressure detected by the pressure sensor 54 when the exhaust valve 56 is closed. The dynamic characteristics Ci1 in FIG. 2 represent the dynamic characteristics of the LSV 46 when the LSV current I is increased at a sweep speed V1 (A / sec). The dynamic characteristics Cd1 in FIG. 2 represent the dynamic characteristics of the LSV 46 when the LSV current I is decreased at a sweep speed −V1 (A / sec). Note that the absolute value of the sweep speed V1 is equal to the absolute value of the sweep speed −V1. As shown in FIG. 2, the dynamic characteristics Ci1 when the LSV current I increases and the dynamic characteristics Cd1 when the LSV current I decreases are different. In other words, the LSV 46 has hysteresis characteristics.

[0030] First, the dynamic characteristic Ci1 will be described. When the LSV current I is zero, the LSV 46 is fully closed, and hydrogen gas does not flow through the hydrogen gas supply path 42. In this state, the pressure P is at its minimum value PL. When the LSV current I is increased, if the LSV current I is less than the current Ia, the LSV 46 is maintained in its fully closed state, and the pressure P is maintained at its minimum value PL. When the LSV current I increases to the current Ia, the LSV 46 begins to open, and the pressure P begins to rise. Hereinafter, the current Ia at which the pressure P begins to rise may be referred to as the rising current Ia. When the LSV current I exceeds the rising current Ia, the opening of the LSV 46 increases as the LSV current I increases, and the pressure P rises. When the LSV current I increases to the current Ib, the LSV 46 is fully open, and the pressure P reaches its maximum value PH. Even if the LSV current I becomes higher than the current Ib, the pressure P does not rise from the maximum value PH.

[0031] Next, the dynamic characteristic Cd1 will be described. When the LSV current I is higher than the current Ib, the LSV 46 is fully open, and the pressure P is at its maximum value PH. When the LSV current I is reduced, the LSV 46 remains fully open even after the LSV current I is reduced to the current Ib. When the LSV current I is reduced, the LSV 46 begins to close and the pressure P begins to decrease when the LSV current I is reduced to a current Ic that is lower than the current Ib. Hereinafter, the current Ic at which the pressure P begins to decrease may be referred to as the falling current Ic. When the LSV current I falls below the falling current Ic, the opening of the LSV 46 decreases as the LSV current I decreases, and the pressure P decreases. When the LSV current I is reduced, the LSV 46 enters a fully closed state and the pressure P reaches its minimum value PL when the LSV current I is reduced to a current Id that is lower than the rising current Ia.

[0032] Also, the dynamic characteristics Ci2 to Ci4 in FIG. 2 show the dynamic characteristics of LSV46 when increasing the LSV current I at a sweep rate different from the sweep rate V1 of the dynamic characteristic Ci1. The dynamic characteristic Ci2 is the dynamic characteristic when increasing the LSV current I at the sweep rate V2, the dynamic characteristic Ci3 is the dynamic characteristic when increasing the LSV current I at the sweep rate V3, and the dynamic characteristic Ci4 is the dynamic characteristic when increasing the LSV current I at the sweep rate V4. The sweep rates V1 to V4 satisfy the relationship V1 < V2 < V3 < V4. As shown in FIG. ②, as the sweep rate increases, the graph shifts to the right, and the LSV current I required to increase the pressure P becomes higher. For example, as the sweep rate increases, the rising current Ia becomes higher. Thus, the dynamic characteristics of LSV46 when the LSV current I increases change according to the sweep rate.

[0033] Also, the dynamic characteristics Cd2 to Cd4 in FIG. 2 show the dynamic characteristics of LSV46 when decreasing the LSV current I at a sweep rate different from the sweep rate -V1 of the dynamic characteristic Cd1. The dynamic characteristic Cd2 is the dynamic characteristic when decreasing the LSV current I at the sweep rate -V2, the dynamic characteristic Cd3 is the dynamic characteristic when decreasing the LSV current I at the sweep rate -V3, and the dynamic characteristic Cd4 is the dynamic characteristic when decreasing the LSV current I at the sweep rate -V4. The sweep rates -V1 to -V4 satisfy the relationship -V4 < -V3 < -V2 < -V1. That is, the sweep rate -V1 means decreasing the LSV current I at the slowest decrease rate among the sweep rates -V1 to -V4, and the sweep rate -V4 means decreasing the LSV current I at the fastest decrease rate among the sweep rates -V1 to -V4. As shown in FIG. 2, as the decrease rate of the LSV current I increases, the graph shifts to the left, and the LSV current I required to decrease the pressure P becomes lower. For example, as the decrease rate of the LSV current I increases, the falling current Ic becomes lower. Thus, the dynamic characteristics of LSV46 when the LSV current I decreases change according to the sweep rate.

[0034] Furthermore, the dynamic characteristics of the LSV 46 vary from one individual to another due to factors such as manufacturing errors and changes over time. The control circuit 48 executes a learning process that measures and stores the dynamic characteristics of the LSV 46. The learning process executed by the control circuit 48 is described below. Note that the exhaust valve 56 is closed during the following learning process. Therefore, the pressure sensor 54 detects the pressure P in the supply path 42c during the learning process.

[0035] FIG. 3 shows the learning process. The control circuit 48 performs the learning process if the learning process has not been performed yet. By performing the learning process by the control circuit 48, the dynamic characteristics of the LSV 46 can be identified even if the dynamic characteristics of the LSV 46 deviate from the design values ​​due to manufacturing errors. Furthermore, even if the learning process has already been performed, the control circuit 48 may periodically perform the learning process shown in FIG. 3. By performing the learning process by the control circuit 48 periodically, the dynamic characteristics of the LSV 46 can be accurately identified even if the dynamic characteristics of the LSV 46 change over time.

[0036] In step S2, the control circuit 48 sets a measurement region R by dividing the usable range of the LSV current I at equal intervals, as shown in FIGS.

[0037] Next, the control circuit 48 repeatedly executes steps S4 to S12. In step S4, the control circuit 48 selects a sweep speed V of the LSV current I. Here, the control circuit 48 selects one sweep speed from a plurality of predetermined positive sweep speeds (for example, sweep speeds V1 to V4).

[0038] In step S6, the control circuit 48 measures the dynamic characteristics of the LSV 46 while increasing the LSV current I at the sweep speed V selected in the previous step S4. More specifically, the control circuit 48 monitors the pressure P detected by the pressure sensor 54 while increasing the LSV current I at the sweep speed V selected in step S4. At this time, the control circuit 48 measures and stores the LSV current I and the pressure P in each measurement region R set in step S2. FIG. 4 shows changes in the LSV current I and the pressure P when step S6 is performed at the sweep speed V. As shown in FIG. 4, each equally divided range of the usable range of the LSV current I is set as a measurement region R. As shown in FIG. 4, the control circuit 48 increases the LSV current I from 0 A at the sweep speed V. When the LSV current I is within each measurement region R, the control circuit 48 measures and stores the LSV current I and the pressure P at that time. For example, the control circuit 48 may measure and store the LSV current I and pressure P when the LSV current I reaches the median value in each measurement region R. Alternatively, the control circuit 48 may measure the LSV current I and pressure P multiple times within one measurement region R and store the average or median values ​​as the LSV current I and pressure P for that measurement region R. By storing the LSV current I and pressure P in each measurement region R in this manner, the control circuit 48 stores each coordinate point U shown in FIG. 4. The control circuit 48 determines the dynamic characteristic Ci of the LSV 46 when the LSV current I is increased based on each coordinate point U. For example, the control circuit 48 may determine the dynamic characteristic Ci of the LSV 46 by connecting each coordinate point U with a straight line or a curve. Alternatively, the control circuit 48 may determine the dynamic characteristic Ci of the LSV 46 by calculating an approximation curve from each coordinate point U.

[0039] In step S6, while the pressure P is greater than the minimum value PL, hydrogen is supplied to the fuel cell stack 20. In step S6, the control circuit 48 supplies oxygen to the fuel cell stack 20 by the oxygen gas supply device 30 in conjunction with the supply of hydrogen to the fuel cell stack 20. Therefore, power is generated in the fuel cell stack 20. The power generated in the fuel cell stack 20 is supplied to the battery 70. Therefore, the battery 70 is charged. In addition, if there is a power demand in the motor 76 or the auxiliary equipment 78, the power generated in the fuel cell stack 20 may be supplied to the motor 76 or the auxiliary equipment 78.

[0040] In step S8, the control circuit 48 selects a sweep speed V of the LSV current I. Here, the control circuit 48 selects one sweep speed from among a plurality of predetermined negative sweep speeds (for example, sweep speeds -V1 to -V4).

[0041] In step S10, the control circuit 48 measures the dynamic characteristics of the LSV 46 while decreasing the LSV current I at the sweep speed V selected in the previous step S8. More specifically, the control circuit 48 monitors the pressure P detected by the pressure sensor 54 while decreasing the LSV current I at the sweep speed V selected in step S8. At this time, the control circuit 48 measures and stores the LSV current I and the pressure P in each measurement region R set in step S2. FIG. 5 shows changes in the LSV current I and the pressure P when step S10 is performed at the sweep speed V (e.g., sweep speed -V1, -V2, -V3, or -V4). As shown in FIG. 5, the control circuit 48 decreases the LSV current I from its maximum value at the sweep speed V. When the LSV current I is within each measurement region R, the control circuit 48 measures and stores the LSV current I and the pressure P at that time. In this way, the control circuit 48 stores the LSV current I and pressure P in each measurement region R, and thereby stores each coordinate point U shown in Fig. 5. Based on each coordinate point U, the control circuit 48 determines the dynamic characteristic Cd of the LSV 46 when the LSV current I is reduced.

[0042] In step S10, while the pressure P is greater than the minimum value PL, hydrogen is supplied to the fuel cell stack 20. In step S10, the control circuit 48 supplies oxygen to the fuel cell stack 20 by the oxygen gas supply device 30 in conjunction with the supply of hydrogen to the fuel cell stack 20. Therefore, power is generated in the fuel cell stack 20. The power generated in the fuel cell stack 20 is supplied to the battery 70, etc.

[0043] In step S12, the control circuit 48 determines whether or not the dynamic characteristics when the LSV current I changes have been measured for all of a plurality of predetermined sweep speeds (for example, sweep speeds V1 to V4 and -V1 to -V4). If there are any sweep speeds for which the dynamic characteristics when the LSV current I changes have not been measured (i.e., NO in step S12), the control circuit 48 executes steps S4 to S12 again. In step S4 from the second time onwards, the control circuit 48 selects one sweep speed from among the sweep speeds for which the measurement of the dynamic characteristics when the LSV current I increases has not been completed. In step S8 from the second time onwards, the control circuit 48 selects one sweep speed from among the sweep speeds for which the measurement of the dynamic characteristics when the LSV current I decreases has not been completed. Therefore, the control circuit 48 repeats steps S4 to S12 multiple times to measure the dynamic characteristics when the LSV current I changes for all of the predetermined positive sweep speeds (e.g., sweep speeds V1 to V4) and negative sweep speeds (e.g., sweep speeds -V1 to -V4). For example, the actual measured values ​​of the dynamic characteristics Ci1 to Ci4 and Cd1 to Cd4 in FIG. 2 are measured and stored by the control circuit 48.

[0044] By performing the above learning process, the control circuit 48 stores the dynamic characteristics when the LSV current I increases at multiple sweep speeds and the dynamic characteristics when the LSV current I decreases at multiple sweep speeds. After the learning process, the control circuit 48 controls the LSV 46 according to the stored dynamic characteristics. For example, while the vehicle is running, a target value of the pressure P is input to the control circuit 48 according to the target power generation amount of the fuel cell stack 20. The control circuit 48 then calculates the sweep speed according to the target value of the pressure P and the current pressure P. Furthermore, the control circuit 48 selects an appropriate dynamic characteristic from the stored dynamic characteristics (e.g., Ci1 to Ci4, Cd1 to Cd4) based on the calculated sweep speed. For example, if the calculated sweep speed is a positive value, the control circuit 48 selects one dynamic characteristic corresponding to the sweep speed from the dynamic characteristics Ci when the LSV current I is increased. Furthermore, if the calculated sweep speed is a negative value, the control circuit 48 selects one dynamic characteristic Cd corresponding to the sweep speed from among the dynamic characteristics Cd used when decreasing the LSV current I. After selecting the dynamic characteristic, the control circuit 48 calculates a target value for the LSV current I based on the selected dynamic characteristic and the target value for the pressure P. The control circuit 48 then changes the LSV current I to the target value at the calculated sweep speed. Because the dynamic characteristics stored in the control circuit 48 are dynamic characteristics actually measured in the learning process, the control circuit 48 can accurately control the pressure P to the target value by controlling the LSV current I as described above. Furthermore, because the dynamic characteristics are measured for each sweep speed in the learning process, the control circuit 48 can control the LSV current I in accordance with changes in the dynamic characteristics due to the sweep speed. For example, when increasing the pressure P, the pressure P can be accurately controlled without being affected by the difference between the dynamic characteristics when the sweep speed is fast and the dynamic characteristics when the sweep speed is slow. Furthermore, when the pressure P is reduced, it is possible to accurately control the pressure P without being affected by the difference in dynamic characteristics between when the sweep speed is fast and when the sweep speed is slow.Furthermore, when the pressure P is changed, the pressure P can be accurately controlled without being affected by the difference between the dynamic characteristics when increasing the pressure P and the dynamic characteristics when decreasing the pressure P (i.e., the influence of hysteresis characteristics). Thus, according to the fuel cell system 10 of the embodiment, the pressure P of the hydrogen gas supplied to the fuel cell stack 20 can be controlled more accurately than conventionally.

[0045] In the above-described embodiment, the dynamic characteristics were alternately measured when increasing the LSV current I and when decreasing the LSV current I. However, it is also possible to measure multiple dynamic characteristics when increasing the LSV current I, and then measure multiple dynamic characteristics when decreasing the LSV current I.

[0046] In the above-described embodiment, the dynamic characteristics are measured at multiple sweep speeds when the LSV current I is increased, and at multiple sweep speeds when the LSV current I is decreased. However, in other embodiments, the dynamic characteristics may be measured at multiple sweep speeds when the LSV current I is increased, but not when the LSV current I is decreased. This configuration still allows accurate control of the pressure P when the LSV current I is increased. In yet another embodiment, the dynamic characteristics may be measured at multiple sweep speeds when the LSV current I is decreased, but not when the LSV current I is increased. This configuration still allows accurate control of the pressure P when the LSV current I is decreased. In yet another embodiment, the dynamic characteristics may be measured at one sweep speed when the LSV current I is increased, and at one sweep speed when the LSV current I is decreased. In this case, the absolute value of the sweep speed when the LSV current I is increased (i.e., the positive sweep speed) may be equal to the absolute value of the sweep speed when the LSV current I is decreased (i.e., the negative sweep speed). Even with this configuration, the pressure P can be controlled without being affected by the hysteresis characteristic.

[0047] In the above embodiment, the control of the LSV 46 has been described, but other solenoid valves (for example, rotary solenoid valves, etc.) may be used instead of the LSV 46.

[0048] Furthermore, in the above-described embodiment, the fuel cell system is mounted on an electric vehicle, but the technology disclosed in this specification may be applied to other fuel cell systems such as stationary types.

[0049] In the above-described embodiment, the number of measurement points at which the LSV current I and the pressure P are measured during measurement of the dynamic characteristics is preferably three or more, and more preferably five or more.

[0050] When focusing on multiple dynamic characteristics when increasing the LSV current I, the sweep speed V1 in the embodiment is an example of a first sweep speed, and the sweep speeds V2 to V4 in the embodiment are examples of a second sweep speed. When focusing on multiple dynamic characteristics when decreasing the LSV current I, the sweep speed -V1 in the embodiment is an example of a first sweep speed, and the sweep speeds -V2 to -V4 in the embodiment are examples of a second sweep speed. When focusing on the dynamic characteristics when increasing the LSV current I and the dynamic characteristics when decreasing the LSV current I, the sweep speed V1 in the embodiment is an example of a first sweep speed, and the sweep speeds -V1 to -V4 in the embodiment are examples of a second sweep speed.

[0051] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0052] 10: Fuel cell system 20: Fuel cell stack 32: Oxygen gas supply channel 42: Hydrogen gas supply channel 46: Linear solenoid valve 48: Control circuit 54: Pressure sensor

Claims

1. A fuel cell system, comprising: A fuel cell; a hydrogen gas supply channel for supplying hydrogen gas to the fuel cell; a solenoid valve for changing the opening degree of the hydrogen gas supply passage; a pressure sensor for detecting a pressure in a downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell; a control circuit for controlling the solenoid valve; and The control circuit a step of detecting and storing the energization current and the pressure at a plurality of points while changing the energization current of the solenoid valve at a first sweep speed; detecting and storing the energizing current and the pressure at a plurality of points while changing the energizing current at a second sweep speed different from the first sweep speed; Run In the step of changing the energizing current at the first sweep speed, the control circuit increases the energizing current at the first sweep speed from a state in which the solenoid valve is closed; In the step of changing the energizing current at the second sweep speed, the control circuit increases the energizing current at the second sweep speed from a state in which the solenoid valve is closed. Fuel cell system.

2. A fuel cell system, A fuel cell; a hydrogen gas supply channel for supplying hydrogen gas to the fuel cell; a solenoid valve for changing the opening degree of the hydrogen gas supply passage; a pressure sensor for detecting a pressure in a downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell; a control circuit for controlling the solenoid valve; and The control circuit a step of detecting and storing the energization current and the pressure at a plurality of points while changing the energization current of the solenoid valve at a first sweep speed; detecting and storing the energizing current and the pressure at a plurality of points while changing the energizing current at a second sweep speed different from the first sweep speed; Run In the step of changing the energizing current at the first sweep speed, the control circuit reduces the energizing current at the first sweep speed from a state in which the solenoid valve is open; In the step of changing the energizing current at the second sweep speed, the control circuit reduces the energizing current at the second sweep speed from a state in which the solenoid valve is open. Fuel cell system.

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