Fuel cell system

Abstract

To learn the characteristics of a solenoid valve used for a fuel cell system with ease.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. The control circuit executes the following steps of: detecting rising of the pressure detected by the pressure sensor when an application current of the solenoid valve is increased from a state where the solenoid valve is closed, and detecting a rising current that is the application current at rising of the pressure; and calculating an increase characteristic that is a relation between the application current and the pressure when the application current is increased on the basis of the rising current.SELECTED DRAWING: Figure 5

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 the brake fluid of a vehicle. The control circuit that controls the solenoid valve stores an initial driving amount as the current value for driving the solenoid valve. The control circuit stores the initial driving amount according to the differential pressure between the upstream side and the downstream side of the solenoid valve. When operating the solenoid valve, the control circuit first sends a current of the initial driving amount to the solenoid valve. [[ID=[]]

[0003] There are individual variations in the characteristics of the solenoid valve. Also, the characteristics of the solenoid valve change due to temperature, changes over time, etc. In contrast, in Patent Document 1, the control circuit corrects the initial driving amount. Specifically, when the control circuit is controlling the brake pressure to the target pressure, it measures the current value flowing through the solenoid valve. Then, based on the measured current value, it corrects the stored initial driving amount.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology of Patent Document 1, when the brake pressure is controlled to the target pressure, an appropriate current value of the solenoid valve is measured and the initial driving amount is corrected. Since the appropriate initial driving amount varies depending on the differential pressure, it is necessary to measure an appropriate current value for each differential pressure and correct the initial driving amount. This specification proposes a technology that can more easily learn the characteristics of the solenoid valve used in a fuel cell system.

Means for Solving the Problems

[0006] (Form 1) A fuel cell system of Embodiment 1 disclosed herein includes a fuel cell, a hydrogen gas supply path for supplying hydrogen gas to the fuel cell, a solenoid valve for changing the opening degree of the hydrogen gas supply path, a pressure sensor for detecting the pressure in the downstream supply path from the solenoid valve to the fuel cell, and a control circuit for controlling the solenoid valve. The control circuit performs the steps of detecting the rise in pressure detected by the pressure sensor when the current supplying the solenoid valve is increased from a closed state and detecting the rise current, which is the current supplying the valve at the time of the pressure rise, and calculating an increase characteristic, which is the relationship between the current supplying the valve and the pressure when the current supplying the valve increases, based on the rise current.

[0007] This fuel cell system detects the rising current of the solenoid valve. By detecting the rising current, the increase characteristic, which is the relationship between the current and pressure when the solenoid valve opens, can be calculated with relatively high accuracy. Thus, this fuel cell system allows for easy calculation of the increase characteristic. [Brief explanation of the drawing]

[0008] [Figure 1] Block diagram of a fuel cell system. [Figure 2] A graph showing the hysteresis characteristics of LSV. [Figure 3] A graph showing the correction of the increasing characteristics of LSV. [Figure 4] A graph showing the correction of the LSV reduction characteristics. [Figure 5] A flowchart showing the learning process in Example 1. [Figure 6] A flowchart illustrating the learning process in Example 2. [Figure 7] A graph showing the correction of the LSV increase characteristics for each sweep speed. [Figure 8]A graph showing the correction of the LSV reduction characteristics for each sweep speed. [Modes for carrying out the invention]

[0009] (Form 2) In the fuel cell system of Embodiment 1, the control circuit may store the standard increase characteristics of the solenoid valve and calculate the increase characteristics by correcting the standard increase characteristics based on the rise current.

[0010] This configuration allows for the calculation of growth characteristics with high accuracy.

[0011] (Form 3) In a fuel cell system of form 1 or 2, the control circuit may perform the steps of: detecting the pressure fall rate detected by the pressure sensor when the energizing current is reduced from the state in which the solenoid valve is open, and detecting the falling current, which is the energizing current at the time the pressure falls; and calculating a decrease characteristic, which is the relationship between the energizing current and the pressure when the energizing current decreases, based on the falling current.

[0012] With this configuration, the decrease characteristic can be easily calculated based on the falling current. Furthermore, solenoid valves may have hysteresis characteristics, and their increase and decrease characteristics may differ. This configuration allows for the calculation of both the increase and decrease characteristics.

[0013] (Form 4) In the fuel cell system of Embodiment 3, the control circuit may store the standard decay characteristics of the solenoid valve and calculate the decay characteristics by correcting the standard decay characteristics based on the falling current.

[0014] This configuration allows for the calculation of reduction characteristics with high accuracy.

[0015] (Form 5) In any of the fuel cell systems of Forms 1 to 4, an exhaust valve for discharging hydrogen gas in the downstream supply path to the outside may be further provided. The control circuit may execute the step of detecting the rising current with the exhaust valve closed.

[0016] According to this configuration, the increase characteristics can be calculated more accurately.

[0017] (Form 6) Any of the fuel cell systems of Forms 1 to 5 may further have a battery. In this case, the battery may be charged by the power generated by the fuel cell in the step of detecting the rising current.

[0018] According to this configuration, even when there is no power demand, the rising current can be detected while supplying hydrogen gas to the fuel cell for power generation.

[0019] (Form 7) In any of the fuel cell systems of Forms 1 to 6, the step of detecting the rising current may include a step of detecting a first rising current, which is the rising current when increasing the energization current at a first sweep speed, and a step of detecting a second rising current, which is the rising current when increasing the energization current at a second sweep speed. In this case, the step of calculating the increase characteristics may include a step of calculating a first increase characteristic, which is the increase characteristic at the first sweep speed, based on the first rising current, and a step of calculating a second increase characteristic, which is the increase characteristic at the second sweep speed, based on the second rising current.

[0020] According to this configuration, even when the increase characteristics vary depending on the sweep speed at which the energization current is increased, the increase characteristics can be calculated for each sweep speed.

[0021] The fuel cell system 10 in the embodiment shown in Figure 1 is mounted on an electric vehicle. The electric vehicle has a motor 76. The motor 76 operates using electricity generated by the fuel cell system 10 to rotate the vehicle's drive wheels.

[0022] The fuel cell system 10 includes 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 passage 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 passage 32. The hydrogen gas supply device 40 has a hydrogen gas supply passage 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 passage 42. Within the fuel cell stack 20, the oxygen gas supplied by the oxygen gas supply passage 32 and the hydrogen gas supplied by the hydrogen gas supply passage 42 react. This generates electricity in the fuel cell stack 20.

[0023] 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 from 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 operates the motor 76 by converting the DC voltage supplied from the fuel cell stack 20 or the battery 70 into an AC voltage and supplying it to 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 operates the auxiliary equipment 78 by converting the DC voltage supplied from the fuel cell stack 20 or the battery 70 into a lower voltage and supplying it to the auxiliary equipment 78.

[0024] 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.

[0025] The hydrogen gas supply source 44 is connected to the upstream end of the hydrogen gas supply line 42. The hydrogen gas supply source 44 is composed of, for example, a hydrogen gas tank. The hydrogen gas supply source 44 supplies high-pressure hydrogen gas to the hydrogen gas supply line 42.

[0026] The LSV46 and 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 LSV46. Downstream of the ejector 50, the hydrogen gas supply channel 42 passes through the inside of the fuel cell stack 20. The hydrogen gas supplied from the hydrogen gas source 44 passes through the LSV46, ejector 50, and fuel cell stack 20 in that order. Hereafter, the portion of the hydrogen gas supply channel 42 upstream of the LSV46 will be referred to as supply channel 42a. Hereafter, the portion of the hydrogen gas supply channel 42 between the LSV46 and ejector 50 will be referred to as supply channel 42b. Hereafter, the portion of the hydrogen gas supply channel 42 between the ejector 50 and fuel cell stack 20 will be referred to as supply channel 42c. Hereafter, the portion of the hydrogen gas supply channel 42 downstream of the fuel cell stack 20 will be referred to as supply channel 42d.

[0027] LSV46 is a valve that opens and closes the hydrogen gas supply passage 42. A control circuit 48 is electrically connected to LSV46. The control circuit 48 controls the current flowing through LSV46 (hereinafter referred to as LSV current I). The degree to which LSV46 opens changes according to the LSV current I. When no LSV current I is flowing, LSV46 is closed. The higher the LSV current I, the greater the degree to which LSV46 opens. When LSV46 is open, hydrogen gas flows from supply passage 42a through LSV46 to supply passage 42b.

[0028] An off-gas circulation path 58 is connected to the ejector 50. Off-gas, which is hydrogen gas that has passed through the fuel cell stack 20, flows through the off-gas circulation path 58. Off-gas is supplied from the off-gas circulation path 58 to the ejector 50. The ejector 50 adds off-gas to the hydrogen gas supplied from the supply path 42b and injects it into the supply path 42c.

[0029] Hydrogen gas injected from the ejector 50 into the supply channel 42c flows into the fuel cell stack 20. Inside the fuel cell stack 20, the hydrogen gas reacts with oxygen gas. 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 channel 42d.

[0030] The gas-liquid separator 52 is connected to the downstream end of the supply passage 42d. The gas-liquid separator 52 is also connected to an off-gas circulation passage 58 and a discharge passage 60. The gas-liquid separator 52 removes moisture from the off-gas supplied from the supply passage 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 passage 60. The gas-liquid separator 52 also supplies the off-gas, from which the moisture has been removed, to the off-gas circulation passage 58. Therefore, as described above, off-gas is supplied to the ejector 50 from the off-gas circulation passage 58.

[0031] A branch line 62 is connected to the supply line 42c. The branch line 62 is equipped with a pressure sensor 54 and an exhaust valve 56. When the exhaust valve 56 is open, the branch line 62 is connected to the outside (i.e., the atmosphere). When the exhaust valve 56 is closed, the pressure of the hydrogen gas in the branch line 62 is equal to the pressure of the hydrogen gas in the supply line 42c. The pressure sensor 54 detects the pressure in the branch line 62. When the exhaust valve 56 is closed, the pressure detected by the pressure sensor 54 is equal to the pressure in the supply line 42c.

[0032] When the fuel cell system 10 generates electricity, the control circuit 48 opens the LSV 46 to a predetermined opening. As a result, hydrogen gas is supplied to the fuel cell stack 20 via the hydrogen gas supply passage 42. Oxygen gas is also supplied to the fuel cell stack 20 via the oxygen gas supply passage 32. Inside the fuel cell stack 20, the hydrogen gas and oxygen gas react to generate electricity. The electricity generated in the fuel cell stack 20 is supplied to the battery 70, the motor drive circuit 72, or the auxiliary drive circuit 74 as needed.

[0033] Figure 2 shows the characteristics of LSV46. The horizontal axis of Figure 2 represents the LSV current I, and the vertical axis represents the pressure P in the supply path 42c. Note that pressure P is equal to the pressure detected by the pressure sensor 54 when the exhaust valve 56 is closed. As shown in Figure 2, LSV46 has hysteresis characteristics. That is, in LSV46, the increasing characteristic Ci1 when the LSV current I increases and the decreasing characteristic Cd1 when the LSV current I decreases are different.

[0034] First, let's explain the case where the LSV current I is increased (i.e., the increasing characteristic Ci1). When the LSV current I is zero, the LSV 46 is fully closed, and no hydrogen gas flows into the hydrogen gas supply passage 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 current Ia1, the LSV 46 remains fully closed, and the pressure P remains at its minimum value PL. When the LSV current I increases to current Ia1, the LSV 46 begins to open, and the pressure P begins to rise. Hereafter, the LSV current I at the point when the pressure P begins to rise may be referred to as the rising current. When the LSV current I exceeds the rising current Ia1, the opening of the LSV 46 increases as the LSV current I increases, and the pressure P increases. When the LSV current I increases to current Ib1, the LSV 46 becomes fully open, and the pressure P reaches its maximum value PH. Even if the LSV current I becomes higher than current Ib1, the pressure P does not rise above the maximum value PH.

[0035] Next, we will explain the case where the LSV current I is reduced (i.e., the reduction characteristic Cd1). When the LSV current I is higher than current Ib1, LSV46 is fully open, and the pressure P is at its maximum value PH. When the LSV current I is reduced, LSV46 remains fully open even when the LSV current I decreases to current Ib1. When the LSV current I is reduced, LSV46 begins to close when it decreases to current Ic1, which is lower than current Ib1, and the pressure P begins to decrease. In the following, the LSV current I at the point when the pressure P begins to decrease may be referred to as the falling current. When the LSV current I falls below the falling current Ic1, the opening of LSV46 decreases as the LSV current I decreases, and the pressure P decreases. When the LSV current I is reduced, LSV46 becomes fully closed when it decreases to current Id1, which is lower than the rising current Ia1, and the pressure P reaches its minimum value PL.

[0036] As explained above, the LSV46 has different characteristics when the LSV current I increases and when the LSV current I decreases.

[0037] The control circuit 48 stores the standard increase characteristic Ci2 shown in Figure 3 and the standard decrease characteristic Cd2 shown in Figure 4. The standard increase characteristic Ci2 is the design increase characteristic of the LSV46, and the standard decrease characteristic Cd2 is the design decrease characteristic of the LSV46. The actual increase characteristic Ci1 and decrease characteristic Cd1 of the LSV46 deviate from the standard increase characteristic Ci2 and standard decrease characteristic Cd2 due to the effects of manufacturing variations and changes over time. Therefore, the control circuit 48 performs a learning process to correct the standard increase characteristic Ci2 and standard decrease characteristic Cd2 and calculate a corrected increase characteristic Ci3 and corrected decrease characteristic Cd3 that are closer to the actual increase characteristic Ci1 and decrease characteristic Cd1. The following describes an example of the learning process performed by the control circuit 48. Note that the exhaust valve 56 is closed during the execution of the learning process in each of the following examples. Therefore, the pressure sensor 54 detects the pressure P in the supply passage 42c during the execution of the learning process in each example. [Examples]

[0038] Figure 5 shows the learning process of Embodiment 1. The control circuit 48 receives power generation requests from an external source as needed. For example, a power generation request is input to the control circuit 48 when the motor 76 or auxiliary equipment 78 is operating, or when the remaining charge of the battery 70 falls below a reference value. The control circuit 48 periodically executes step S2 to check whether a power generation request has been input. When the control circuit 48 receives a power generation request, it determines YES in step S2 and executes step S4.

[0039] In step S4, the control circuit 48 determines whether or not the learning process has been performed. If the learning process has not been performed, the control circuit 48 determines NO in step S4 and executes step S6.

[0040] In step S6, the control circuit 48 monitors the pressure P detected by the pressure sensor 54 while gradually increasing the LSV current I from 0A. During the execution of step S6, the control circuit 48 determines in step S8 whether or not the pressure P has risen from the minimum value PL. The control circuit 48 repeats step S8 until the pressure P rises from the minimum value PL. When the pressure P rises from the minimum value PL, the control circuit 48 determines YES in step S8. Then, in step S10, the control circuit 48 stores the LSV current I at the time the pressure P rose from the minimum value PL as the rising current Ia1.

[0041] For example, in step S6, as shown by arrow 100 in Figure 3, the control circuit 48 gradually increases the LSV current I from 0A. While the LSV current I is low, the pressure P detected by the pressure sensor 54 does not rise above the minimum value PL. When the LSV current I rises to the actual rise current Ia1 of the LSV 46, the pressure P begins to rise. Therefore, the control circuit 48 determines YES in step S8 at the timing when the pressure P begins to rise, and stores the rise current Ia1 in step S10. As shown in Figure 3, in many cases the rise current Ia1 detected in step S10 does not match the rise current Ia2 of the standard increase characteristic Ci2.

[0042] Next, in step S12, the control circuit 48 corrects the standard increase characteristic Ci2 based on the detected rise current Ia1. This allows the control circuit 48 to calculate the corrected increase characteristic Ci3. In one example, as shown in Figure 3, the control circuit 48 calculates the difference ΔIa (=Ia1-Ia2) between the rise currents Ia1 and Ia2, and calculates the corrected increase characteristic Ci3 by adding this difference ΔIa to the LSV current I values ​​at each coordinate point of the standard increase characteristic Ci2. That is, the control circuit 48 calculates the corrected increase characteristic Ci3 by shifting the standard increase characteristic Ci2 by a difference ΔIa in the axial direction of the LSV current I. When the corrected increase characteristic Ci3 is calculated in this way, the rise current in the corrected increase characteristic Ci3 matches the actual rise current Ia1 of the LSV46. Furthermore, by calculating the corrected increase characteristic Ci3 in this way, the corrected increase characteristic Ci3 can be matched to the actual increase characteristic Ci1 of the LSV46 with relatively high accuracy. Alternatively, in another example, the ratio X (=Ia1 / Ia2) of the rising current Ia1 and rising current Ia2 can be calculated, and the corrected growth characteristic Ci3 can be calculated by multiplying the value of the LSV current I at each coordinate point of the standard growth characteristic Ci2 by the ratio X. Even when calculating the corrected growth characteristic Ci3 in this way, the corrected growth characteristic Ci3 can be matched to the actual growth characteristic Ci1 of LSV46 with relatively high accuracy.

[0043] Next, in step S14, the control circuit 48 controls the LSV current I to control the pressure P to a target value. Here, the control circuit 48 can control the LSV current I based on the correction increase characteristic Ci3. This ensures that hydrogen gas is supplied to the fuel cell stack 20 at the appropriate pressure, and that the fuel cell stack 20 generates electricity. The power generated in the fuel cell stack 20 is supplied to the battery 70, the motor drive circuit 72, or the auxiliary drive circuit 74.

[0044] When power generation begins in the fuel cell stack 20, the control circuit 48 repeatedly executes step S16 to check whether a power generation stop request has been input from an external source. When the control circuit 48 receives a power generation stop request, it determines YES in step S16 and executes step S18.

[0045] In step S18, the control circuit 48 monitors the pressure P detected by the pressure sensor 54 while gradually decreasing the LSV current I from its maximum value. During the execution of step S18, the control circuit 48 determines in step S20 whether the pressure P has decreased from its maximum value PH. The control circuit 48 repeats step S20 until the pressure P decreases from its maximum value PH. When the pressure P decreases from its maximum value PH, the control circuit 48 determines YES in step S20. Then, in step S22, the control circuit 48 stores the LSV current I at the time the pressure P decreased from its maximum value PH as the falling edge current Ic1.

[0046] For example, in step S18, as shown by arrow 102 in Figure 4, the control circuit 48 gradually decreases the LSV current I from its maximum value. While the LSV current I is high, the pressure P detected by the pressure sensor 54 does not fall below its maximum value PH. When the LSV current I falls to the actual falling current Ic1 of the LSV 46, the pressure P begins to fall. Therefore, the control circuit 48 determines YES in step S20 at the timing when the pressure P begins to fall, and stores the falling current Ic1 in step S22. As shown in Figure 4, in many cases the falling current Ic1 detected in step S22 does not match the falling current Ic2 of the standard decay characteristic Cd2.

[0047] Next, in step S24, the control circuit 48 corrects the standard decay characteristic Cd2 based on the detected falling current Ic1. This allows the control circuit 48 to calculate the corrected decay characteristic Cd3. In one example, as shown in Figure 4, the control circuit 48 calculates the difference ΔIc (=Ic1-Ic2) between the falling currents Ic1 and Ic2, and calculates the corrected decay characteristic Cd3 by adding this difference ΔIc to the LSV current I values ​​at each coordinate point of the standard decay characteristic Cd2. That is, the control circuit 48 calculates the corrected decay characteristic Cd3 by shifting the standard decay characteristic Cd2 by a difference ΔIc in the axial direction of the LSV current I. When the corrected decay characteristic Cd3 is calculated in this way, the falling current in the corrected decay characteristic Cd3 matches the actual falling current Ic1 of the LSV 46. Furthermore, by calculating the corrected decay characteristic Cd3 in this way, the corrected decay characteristic Cd3 can be matched to the actual decay characteristic Cd1 of the LSV 46 with relatively high accuracy. Alternatively, in another example, the ratio X (=Ic1 / Ic2) of the falling currents Ic1 and Ic2 can be calculated, and the corrected reduction characteristic Cd3 can be calculated by multiplying the value of the LSV current I at each coordinate point of the standard reduction characteristic Cd2 by this ratio X. Even when calculating the corrected reduction characteristic Cd3 in this way, it is possible to match the corrected reduction characteristic Cd3 to the actual reduction characteristic Cd1 of LSV46 with relatively high accuracy.

[0048] Next, in step S26, the control circuit 48 reduces the LSV current I to 0A and completely closes the LSV 46. This stops the supply of hydrogen gas to the fuel cell stack 20 and stops power generation by the fuel cell stack 20.

[0049] As described above, the correction increase characteristic Ci3 and the correction decrease characteristic Cd3 are calculated through the learning process in steps S6 to S24. If a power generation request occurs after the learning process has been performed, the control circuit 48 determines YES in step S4 and performs power generation in step S30 without the learning process. Here, the control circuit 48 controls the LSV current I based on the correction increase characteristic Ci3 and the correction decrease characteristic Cd3. This allows for accurate control of the pressure P.

[0050] As described above, in Example 1, the control circuit 48 stores the standard increase characteristic Ci2, and calculates the corrected increase characteristic Ci3 by correcting the standard increase characteristic Ci2 based on the measured rise current Ia1. This method makes it possible to calculate a corrected increase characteristic Ci3 that is close to the actual increase characteristic Ci1 of the LSV 46. Furthermore, this method eliminates the need to measure the correlation between the LSV current I and pressure P at multiple points, making it easy to calculate the corrected increase characteristic Ci3.

[0051] Furthermore, in Example 1, the control circuit 48 stores the standard reduction characteristic Cd2, and calculates the corrected reduction characteristic Cd3 by correcting the standard reduction characteristic Cd2 based on the measured falling current Ic1. This method makes it possible to calculate a corrected reduction characteristic Cd3 that is close to the actual reduction characteristic Cd1 of the LSV 46. In addition, this method does not require measuring the correlation between the LSV current I and pressure P at multiple points, and the corrected reduction characteristic Cd3 can be easily calculated.

[0052] Furthermore, in Example 1, the increasing and decreasing characteristics are corrected independently. As mentioned above, LSV46 has hysteresis characteristics, and its increasing and decreasing characteristics are different. Therefore, by correcting the increasing and decreasing characteristics independently, as in Example 1, these can be appropriately corrected. [Examples]

[0053] Figure 6 shows the learning process of Example 2. The learning process in Example 2 is performed regardless of whether there is a power generation request or not. In step S4, the control circuit 48 determines whether the learning process has been performed or not. If the learning process has been performed, the control circuit 48 determines YES in step S4 and terminates the process in Figure 6. If the learning process has not been performed, the control circuit 48 determines NO in step S4 and executes steps S6 to S12. Steps S6 to S12 in Example 2 are the same as steps S6 to S12 in Example 1. Therefore, in steps S6 to S12 of Example 2, the corrected increase characteristic Ci3 is calculated. That is, similar to Example 1, the control circuit 48 measures the rise current Ia1 and calculates the corrected increase characteristic Ci3 by correcting the standard increase characteristic Ci2 based on the rise current Ia1. Note that if the LSV current I is increased in steps S6 to S12, the output current of the fuel cell stack 20 increases even though there is no power generation request. Here, the battery 70 is charged by supplying the output current of the fuel cell stack 20 to the battery 70.

[0054] Next, the control circuit 48 executes steps S18 to S26. Steps S18 to S26 in Example 2 are the same as steps S18 to S26 in Example 1. Therefore, in steps S18 to S26 of Example 2, the corrected reduction characteristic Cd3 is calculated. That is, in the same manner as in Example 1, the control circuit 48 measures the falling current Ic1 and calculates the corrected reduction characteristic Cd3 by correcting the standard reduction characteristic Cd2 based on the falling current Ic1.

[0055] As described above, according to the configuration of Embodiment 2, the learning process can be executed even when there is no power generation request. After the learning process, the control circuit 48 controls the LSV 46 based on the correction increase characteristic Ci3 and the correction decrease characteristic Cd3. [Examples]

[0056] The rising current Ia1 may increase as the sweep rate of the LSV current I (i.e., the rate at which the LSV current I is changed) increases. For example, as shown in Figure 7, a low rising current Ia1-1 may occur when the sweep rate is slow, a moderate rising current Ia1-2 may occur when the sweep rate is moderate, and a high rising current Ia1-3 may occur when the sweep rate is fast. Also, the falling current Ic1 may decrease as the sweep rate of the LSV current I increases. For example, as shown in Figure 8, a high falling current Ic1-1 may occur when the sweep rate is slow, a moderate falling current Ic1-2 may occur when the sweep rate is moderate, and a low falling current Ic1-3 may occur when the sweep rate is fast. In Example 3, when using such an LSV46, the increasing and decreasing characteristics of the LSV current I are corrected for each sweep rate.

[0057] In Example 3, the control circuit 48 repeatedly executes the learning process multiple times. Each learning process may be executed in response to a power generation request, as in Example 1, or regardless of a power generation request, as in Example 2.

[0058] In the initial learning process, the control circuit 48 detects the rising current Ia1-1 while increasing the LSV current I at a slow sweep rate (e.g., 0.01 A / sec). Upon detecting the rising current Ia1-1, the control circuit 48 calculates the corrected increasing characteristic Ci3-1 by correcting the standard increasing characteristic Ci2 based on the rising current Ia1-1. The control circuit 48 stores the calculated corrected increasing characteristic Ci3-1 as the corrected increasing characteristic at the slow sweep rate. Also in the initial learning process, the control circuit 48 detects the falling current Ic1-1 while decreasing the LSV current I at a slow sweep rate. Upon detecting the falling current Ic1-1, the control circuit 48 calculates the corrected decreasing characteristic Cd3-1 by correcting the standard decreasing characteristic Cd2 based on the falling current Ic1-1. The control circuit 48 stores the calculated corrected decreasing characteristic Cd3-1 as the corrected decreasing characteristic at the slow sweep rate.

[0059] In the second learning process, the control circuit 48 detects the rising current Ia1-2 while increasing the LSV current I at a moderate sweep rate (e.g., 0.05 A / sec). Upon detecting the rising current Ia1-2, the control circuit 48 calculates the corrected rising characteristic Ci3-2 by correcting the standard rising characteristic Ci2 based on the rising current Ia1-2. The control circuit 48 stores the calculated corrected rising characteristic Ci3-2 as the corrected rising characteristic at a moderate sweep rate. Also in the second learning process, the control circuit 48 detects the falling current Ic1-2 while decreasing the LSV current I at a moderate sweep rate. Upon detecting the falling current Ic1-2, the control circuit 48 calculates the corrected decreasing characteristic Cd3-2 by correcting the standard decreasing characteristic Cd2 based on the falling current Ic1-2. The control circuit 48 stores the calculated corrected decreasing characteristic Cd3-2 as the corrected decreasing characteristic at a moderate sweep rate.

[0060] In the third learning process, the control circuit 48 detects the rising current Ia1-3 while increasing the LSV current I at a fast sweep rate (e.g., 0.1 A / sec). Upon detecting the rising current Ia1-3, the control circuit 48 calculates the corrected increasing characteristic Ci3-3 by correcting the standard increasing characteristic Ci2 based on the rising current Ia1-3. The control circuit 48 stores the calculated corrected increasing characteristic Ci3-3 as the corrected increasing characteristic at a fast sweep rate. Also in the third learning process, the control circuit 48 detects the falling current Ic1-3 while decreasing the LSV current I at a fast sweep rate. Upon detecting the falling current Ic1-3, the control circuit 48 calculates the corrected decreasing characteristic Cd3-3 by correcting the standard decreasing characteristic Cd2 based on the falling current Ic1-3. The control circuit 48 stores the calculated corrected decreasing characteristic Cd3-3 as the corrected decreasing characteristic at a fast sweep rate.

[0061] As described above, in Embodiment 3, the control circuit 48 calculates the correction increase characteristic and the correction decrease characteristic for each sweep speed. After the learning process is completed, the control circuit 48 selects the correction increase characteristic and the correction decrease characteristic according to the sweep speed of the LSV current I, and controls the LSV current I according to the selected correction increase characteristic and the correction decrease characteristic. Therefore, the pressure P can be accurately controlled.

[0062] In the above-described Examples 1 to 3, both the increasing and decreasing characteristics were corrected. However, it is also possible to correct only one of the increasing or decreasing characteristics.

[0063] Furthermore, in Examples 1 to 3 described above, the learning process was performed when it had not been performed before. However, even if the learning process has already been performed, it may be performed periodically. By performing the learning process periodically, the corrected increase characteristics and corrected decrease characteristics can be calculated in accordance with the changes in the characteristics of LSV46 over time.

[0064] Furthermore, while the control of the LSV46 was described in Examples 1 to 3 above, other solenoid valves (for example, rotary solenoid valves, etc.) may be used instead of the LSV46.

[0065] Furthermore, although the embodiments described above describe a fuel cell system mounted on an electric vehicle, the technology disclosed herein may also be applied to other fuel cell systems, such as stationary fuel cell systems.

[0066] Furthermore, in the above-described embodiment, the corrected increase characteristic was calculated by correcting the standard increase characteristic based on the rising current. However, the increase characteristic of LSV may also be calculated by other calculation methods based on the rising current. For example, the increase characteristic may be calculated by plotting a graph such that the pressure P increases according to a predetermined function from the coordinate point of the rising current. Furthermore, in the above-described embodiment, the corrected decrease characteristic was calculated by correcting the standard decrease characteristic based on the falling current. However, the decrease characteristic of LSV may also be calculated by other calculation methods based on the falling current. For example, the decrease characteristic may be calculated by plotting a graph such that the pressure P decreases according to a predetermined function from the coordinate point of the falling current.

[0067] Although embodiments have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness. [Explanation of Symbols]

[0068] 10: Fuel cell system 20: Fuel cell stack 32: Oxygen gas supply line 42: Hydrogen gas supply route 46: Linear solenoid valve 48: Control circuit 54: Pressure sensor 56: Exhaust valve

Claims

1. A fuel cell system, Fuel cells and A hydrogen gas supply path for supplying hydrogen gas to the fuel cell, A solenoid valve that changes the opening degree of the hydrogen gas supply passage, A pressure sensor for detecting the pressure in the downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell, The control circuit for controlling the solenoid valve stores a standard increase characteristic which is the relationship between the current and the pressure when the current supplying the solenoid valve is increased, and stores the standard increase characteristic which is the relationship between the current supplying the solenoid valve and the pressure. It has, The control circuit, The steps include detecting the rise in pressure detected by the pressure sensor when the current supplying the solenoid valve is increased from a closed state, and detecting the rise current, which is the current supplying the solenoid valve at the time the pressure rises, A step of calculating the increase characteristic, which is the relationship between the energized current and the pressure when the energized current increases, by adding the value obtained by subtracting the rise current of the standard increase characteristic from the detected rise current to the current value of the standard increase characteristic. A fuel cell system that performs this function.

2. A fuel cell system, Fuel cells and A hydrogen gas supply path for supplying hydrogen gas to the fuel cell, A solenoid valve that changes the opening degree of the hydrogen gas supply passage, A pressure sensor for detecting the pressure in the downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell, The control circuit for controlling the solenoid valve stores a standard increase characteristic which is the relationship between the current and the pressure when the current supplying the solenoid valve is increased, and stores the standard increase characteristic which is the relationship between the current supplying the solenoid valve and the pressure. It has, The control circuit, The steps include detecting the rise in pressure detected by the pressure sensor when the current supplying the solenoid valve is increased from a closed state, and detecting the rise current, which is the current supplying the solenoid valve at the time the pressure rises, A step of calculating the increase characteristic, which is the relationship between the current and the pressure when the current increases, by multiplying the value obtained by dividing the detected rise current by the rise current of the standard increase characteristic by the current value of the standard increase characteristic. A fuel cell system that performs this function.

3. A fuel cell system, Fuel cells and A hydrogen gas supply path for supplying hydrogen gas to the fuel cell, A solenoid valve that changes the opening degree of the hydrogen gas supply passage, A pressure sensor for detecting the pressure in the downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell, Control circuit for controlling the solenoid valve, It has, The control circuit, The steps include detecting the rise in pressure detected by the pressure sensor when the current supplying the solenoid valve is increased from a closed state, and detecting the rise current, which is the current supplying the solenoid valve at the time of the pressure rise, A step of calculating the increasing characteristic, which is the relationship between the current and the pressure when the current increases, by drawing a graph from the coordinate point of the rising current so that the pressure increases according to a predetermined function, A fuel cell system that performs this function.

4. The control circuit, The system stores the standard decrease characteristic, which is the relationship between the current and pressure when the current supplied to the solenoid valve decreases. The steps include detecting the pressure drop detected by the pressure sensor when the current is reduced from the open state of the solenoid valve, and detecting the falling current, which is the current that is energized when the pressure drops, A step of calculating the reduction characteristic, which is the relationship between the current and the pressure when the current decreases, by adding the value obtained by subtracting the falling current of the standard reduction characteristic from the detected falling current to the current value of the standard reduction characteristic. Execute A fuel cell system according to any one of claims 1 to 3.

5. The control circuit, The system stores the standard decrease characteristic, which is the relationship between the current and pressure when the current supplied to the solenoid valve decreases. The steps include detecting the pressure drop detected by the pressure sensor when the current is reduced from the open state of the solenoid valve, and detecting the falling current, which is the current that is energized when the pressure drops, A step of calculating the reduction characteristic, which is the relationship between the current and the pressure when the current decreases, by multiplying the value obtained by dividing the detected falling current by the falling current of the standard reduction characteristic by the current value of the standard reduction characteristic. Execute A fuel cell system according to any one of claims 1 to 3.

6. The control circuit, The steps include detecting the pressure drop detected by the pressure sensor when the current is reduced from the open state of the solenoid valve, and detecting the falling current, which is the current that is energized when the pressure drops, A step of calculating a decrease characteristic, which is the relationship between the current and the pressure when the current decreases, by drawing a graph from the coordinate point of the falling current such that the pressure decreases according to a specific function, Execute A fuel cell system according to any one of claims 1 to 3.

7. The system further includes an exhaust valve for discharging hydrogen gas from the downstream supply channel to the outside. The control circuit performs the step of detecting the rising current with the exhaust valve closed. A fuel cell system according to any one of claims 1 to 3.

8. It also has a battery, The fuel cell system according to any one of claims 1 to 3, wherein in the step of detecting the rising current, the battery is charged with power generated by the fuel cell.

9. The step of detecting the rising current includes a step of detecting a first rising current, which is the rising current when the energizing current is increased at a first sweep speed, and a step of detecting a second rising current, which is the rising current when the energizing current is increased at a second sweep speed. The step of calculating the aforementioned increase characteristic comprises: a step of calculating a first increase characteristic, which is the increase characteristic at the first sweep speed, based on the first rise current; and a step of calculating a second increase characteristic, which is the increase characteristic at the second sweep speed, based on the second rise current. A fuel cell system according to any one of claims 1 to 3.

10. A fuel cell system, Fuel cells and A hydrogen gas supply path for supplying hydrogen gas to the fuel cell, A solenoid valve that changes the opening degree of the hydrogen gas supply passage, A pressure sensor for detecting the pressure in the downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell, The control circuit for controlling the solenoid valve stores a standard decrease characteristic which is the relationship between the current and the pressure when the current supplying the solenoid valve decreases, It has, The control circuit, The steps include detecting the pressure drop detected by the pressure sensor when the current supplied to the solenoid valve is reduced from an open state, and detecting the falling current, which is the current supplied at the time of the pressure drop, A step of calculating the reduction characteristic, which is the relationship between the current and the pressure when the current decreases, by adding the value obtained by subtracting the falling current of the standard reduction characteristic from the detected falling current to the current value of the standard reduction characteristic. A fuel cell system that performs this function.

11. A fuel cell system, Fuel cells and A hydrogen gas supply path for supplying hydrogen gas to the fuel cell, A solenoid valve that changes the opening degree of the hydrogen gas supply passage, A pressure sensor for detecting the pressure in the downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell, The control circuit for controlling the solenoid valve stores a standard decrease characteristic which is the relationship between the current and the pressure when the current supplying the solenoid valve decreases, It has, The control circuit, The steps include detecting the pressure drop detected by the pressure sensor when the current supplied to the solenoid valve is reduced from an open state, and detecting the falling current, which is the current supplied at the time of the pressure drop, A step of calculating the reduction characteristic, which is the relationship between the current and the pressure when the current decreases, by multiplying the value obtained by dividing the detected falling current by the falling current of the standard reduction characteristic by the current value of the standard reduction characteristic. A fuel cell system that performs this function.

12. A fuel cell system, Fuel cells and A hydrogen gas supply path for supplying hydrogen gas to the fuel cell, A solenoid valve that changes the opening degree of the hydrogen gas supply passage, A pressure sensor for detecting the pressure in the downstream supply path of the hydrogen gas supply path from the solenoid valve to the fuel cell, Control circuit for controlling the solenoid valve, It has, The control circuit, The steps include detecting the pressure drop detected by the pressure sensor when the current supplied to the solenoid valve is reduced from an open state, and detecting the falling current, which is the current supplied when the pressure drops; A step of calculating a decrease characteristic, which is the relationship between the current and the pressure when the current decreases, by drawing a graph from the coordinate point of the falling current such that the pressure decreases according to a specific function, A fuel cell system that performs this function.

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