Fuel battery system

Abstract

To provide a fuel battery system capable of maintaining a seal function between a valve seat and a valve body in an on-off value.SOLUTION: According to the present disclosure, in a fuel battery system 1, an air valve 40 comprises a rubber seal part 113a that seals between a valve body 114 and a valve seat 113 when the air valve 40 is in a full closing state. A control part 51 performs a power generation stop full closing control for setting the air valve 40 in the full closing state when the power generation of a fuel battery 11 is stopped. When performing the power generation stop full closing control, an open level of the air valve 40 is set in a control full closing and opening level that is larger than a mechanical closing and opening level as 0°. After that, it is corrected in accordance with a lapse time.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a fuel cell system having a fuel cell that generates electricity by supplying a fuel gas and an oxidant gas, and is particularly suitable for a fuel cell system mounted on a fuel cell vehicle. [Background technology]

[0002] Patent Document 1 discloses a fuel cell system in which, when the fuel cell is stopped, an electromagnetic valve is opened to a certain degree, reactive gas is supplied to the fuel cell, water droplets adhering to the inside of the fuel cell are blown away by the reactive gas and discharged to the outside, and then the electromagnetic valve is driven to a fully closed state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-218242 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an on-off valve such as the solenoid valve disclosed in Patent Document 1, a seal member may be provided between the valve seat and the valve body to obtain a sealing function. Here, in the fuel cell system disclosed in Patent Document 1, when the fuel cell is stopped, the solenoid valve is opened to a certain degree to supply reactant gas to the fuel cell, and then the solenoid valve is fully closed. Here, if the solenoid valve is fully closed at an opening of 0°, the load acting on the seal member increases. Then, repeated opening and closing of the solenoid valve may wear out the seal member, and the seal function between the valve seat and the valve body may not be maintained.

[0005] Therefore, the present disclosure has been made to solve the above-mentioned problems, and has an object to provide a fuel cell system that can maintain the sealing function between the valve seat and the valve body in the on-off valve. [Means for solving the problem]

[0006] One form of the present disclosure made to solve the above problems is a fuel cell system having a fuel cell, an oxidant gas passage connected to the fuel cell and through which an oxidant gas flows, an on-off valve for opening and closing the oxidant gas passage, and a control unit for performing various controls, the on-off valve comprises a valve seat, a valve body that abuts or moves away from the valve seat, and a sealing member provided on either the valve seat or the valve body and that seals between the valve body and the valve seat when the on-off valve is in a fully closed state, and the control unit performs a power generation stop full closure control to bring the on-off valve into a fully closed state when power generation of the fuel cell is stopped, and when performing the power generation stop full closure control, sets the opening degree of the on-off valve to a controlled full closure opening degree that is greater than the mechanical full closure opening degree which is 0°, and then corrects it according to the elapsed time.

[0007] According to this aspect, when power generation by the fuel cell is stopped, the on-off valve is fully closed to prevent oxidant gas from entering the fuel cell. When the on-off valve is fully closed in this manner, the opening degree of the on-off valve is first set to a controlled fully closed opening degree, rather than to a mechanical fully closed opening degree. In this manner, when the on-off valve is fully closed, the opening degree of the on-off valve is set to a controlled fully closed opening degree, at which the load acting on the seal member is suppressed more than that at the mechanical fully closed opening degree, so wear of the seal member can be suppressed. Therefore, the sealing function between the valve seat and the valve body in the on-off valve can be maintained.

[0008] Furthermore, if the internal pressure of the fuel cell changes with a change in the temperature of the fuel cell after power generation by the fuel cell has stopped, negative pressure may occur inside the fuel cell, causing oxidant gas to enter the fuel cell from the oxidant gas passage. Therefore, by correcting the opening of the on-off valve to the mechanical full-close opening side according to the elapsed time after setting it to the controlled full-close opening, the on-off valve can be used to prevent oxidant gas from entering the fuel cell from the oxidant gas passage.

[0009] In the above aspect, it is preferable that the control unit acquires the temperature of the fuel cell and the internal pressure of the fuel cell every predetermined time after power generation of the fuel cell is stopped, and if the amount of change in the internal pressure of the fuel cell due to the change in the temperature of the fuel cell since the last acquisition is less than an estimated amount, it determines that a leak has occurred in the on-off valve and corrects the opening degree of the on-off valve to the mechanical fully closed opening degree side rather than a standard opening degree specified according to the elapsed time.

[0010] According to this aspect, when a leak occurs in the on-off valve, the leak can be detected and stopped. Also, since the opening degree of the on-off valve can be corrected according to the leakage condition of the on-off valve, the opening degree of the on-off valve can be set to an appropriate opening degree that does not apply an excessive load to the seal member.

[0011] In the above aspect, it is preferable that the control unit determines that there is an abnormality in the sealing function of the seal member and issues a warning when the amount of change in the internal pressure of the fuel cell is less than the estimated amount by a predetermined amount or more.

[0012] According to this aspect, an abnormality in the sealing function of the seal member caused by wear of the seal member can be detected, and therefore measures can be taken immediately to restore the sealing function of the seal member.

[0013] In the above aspect, it is preferable that the control unit acquires the temperature of the fuel cell and the internal pressure of the fuel cell every time a predetermined time has elapsed after power generation of the fuel cell has stopped, and if the amount of change in the internal pressure of the fuel cell due to the change in the temperature of the fuel cell since the last acquisition matches or approximately matches an estimated amount, corrects the opening of the opening / closing valve to a standard opening specified in accordance with the elapsed time.

[0014] According to this aspect, the opening degree of the on-off valve can be set to an appropriate opening degree that does not apply an excessive load to the seal member, while the on-off valve can be kept in a fully closed state.

[0015] In the above aspect, it is preferable that the control unit acquires the temperature of the fuel cell and the internal pressure of the fuel cell every predetermined time after power generation of the fuel cell is stopped, and if the change in the internal pressure of the fuel cell due to the change in the temperature of the fuel cell since the last acquisition is greater than an estimated amount, corrects the opening degree of the on-off valve to the opposite side of the mechanical fully closed opening degree from a standard opening degree specified according to the elapsed time.

[0016] According to this aspect, the opening degree of the on-off valve can be set to an appropriate opening degree that does not apply an excessive load to the seal member, while the on-off valve can be kept in a fully closed state.

[0017] In the above aspect, it is preferable that the control unit corrects the opening of the on-off valve based on a standard opening defined according to the elapsed time, updates the standard opening based on the correction history of the opening of the on-off valve when the current power generation stop total closure control is performed, and corrects the opening of the on-off valve based on the updated standard opening when the next power generation stop total closure control is performed.

[0018] According to this aspect, the opening degree of the on-off valve can be appropriately corrected in accordance with the elapsed time.

[0019] In the above aspect, it is preferable that the control unit adjusts the length of the predetermined period of time in accordance with the difference between the temperature of the fuel cell and an outside air temperature.

[0020] According to this aspect, the opening degree of the on-off valve can be controlled to an opening degree corresponding to the change in pressure of the fuel cell, which changes according to the difference between the temperature of the fuel cell and the outside air temperature. Effect of the Invention

[0021] According to the fuel cell system of the present disclosure, the sealing function between the valve seat and the valve body in the on-off valve can be maintained. [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic diagram of a fuel cell system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an external perspective view of the air valve of the present embodiment. [Diagram 3] 1 is a perspective view showing a valve portion in a fully closed state (specifically, a state in which the opening degree of the air valve is a mechanically fully closed opening degree) with a part cut away. FIG. [Figure 4] FIG. 2 is a perspective view showing a valve portion in a fully open state with a part cut away. [Diagram 5] 4 is a side view showing the valve seat, the valve body, and the rotating shaft in the state shown in FIG. 3. [Figure 6] 6 is a cross-sectional view taken along line AA in FIG. 5. [Figure 7] FIG. 4 is a diagram showing the relationship between the opening degree and the opening area of ​​the air valve. [Figure 8] FIG. 13 is a diagram showing how the stack pressure decreases with a decrease in stack temperature after power generation by the fuel cell is stopped and the air valve is fully closed. [Figure 9] 13 is a diagram showing how the surface pressure acting on the rubber seal portion increases by correcting the opening degree of the air valve toward the mechanically fully closed opening degree side according to the elapsed time. FIG. [Figure 10] FIG. 4 is a flow chart showing the contents of control performed in the first embodiment. [Figure 11] FIG. 4 is a flow chart showing the contents of control performed in the first embodiment. [Figure 12] FIG. 4 is a flow chart showing the contents of control performed in the first embodiment. [Figure 13] FIG. 13 is a diagram showing a map defining a controlled fully-closed opening degree (reference opening degree) with respect to a time (elapsed time) after stack-off. [Figure 14] FIG. 11 is a flow chart showing the contents of control performed in the second embodiment. [Figure 15] FIG. 11 is a flow chart showing the contents of control performed in the second embodiment. [Figure 16] FIG. 11 is a flow chart showing the contents of control performed in the second embodiment. [Figure 17] FIG. 13 is a diagram showing a map defining a correction value of the opening degree with respect to a pressure difference from an estimated value. [Figure 18]FIG. 11 is a flow chart showing a part of the contents of the control performed in the third embodiment. [Figure 19] FIG. 13 is a flow chart showing a part of the contents of the control performed in the fourth embodiment. [Figure 20] FIG. 13 is a flow chart showing the contents of control performed in the fifth embodiment. [Figure 21] FIG. 13 is a diagram showing a map of pattern (1) in which a controlled fully-closed opening degree (reference opening degree) is defined with respect to a time (elapsed time) after stack-off. [Figure 22] FIG. 13 is a diagram showing a map of pattern (2) in which a controlled fully-closed opening degree (reference opening degree) is defined with respect to a time (elapsed time) after stack-off. [Figure 23] FIG. 13 is a diagram showing a map of pattern (3) in which a controlled fully-closed opening degree (reference opening degree) is defined with respect to a time (elapsed time) after stack-off. [Figure 24] 13 is a diagram showing how the timing for acquiring the stack temperature and stack pressure is changed depending on the temperature difference between the stack temperature and the outside air temperature. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An embodiment of a fuel cell system according to the present disclosure will now be described.

[0024] <Outline of fuel cell system> The fuel cell system 1 of this embodiment is a system that is mounted on a fuel cell vehicle and supplies power to its drive motor (not shown). As shown in Figure 1, the fuel cell system 1 has a fuel cell 11, a hydrogen supply passage 21, a hydrogen discharge passage 22, an air supply passage 31, and an air discharge passage 32.

[0025] The fuel cell 11 generates power by receiving a supply of fuel gas and an oxidant gas. In this embodiment, the fuel gas is, for example, hydrogen gas, and the oxidant gas is, for example, air. The power generated by the fuel cell 11 is supplied to a drive motor (not shown) via an inverter (not shown).

[0026] The hydrogen supply passage 21 is a passage for supplying hydrogen gas from a hydrogen tank (not shown) to the fuel cell 11. The hydrogen discharge passage 22 is a passage for discharging hydrogen gas from the fuel cell 11.

[0027] The air supply passage 31 is a passage that is connected to the fuel cell 11 and through which air flows, and is a passage for supplying air from the outside of the fuel cell system 1 to the fuel cell 11. The air discharge passage 32 is a passage that is connected to the fuel cell 11 and through which air flows, and is a passage for discharging air from the fuel cell 11. The air supply passage 31 and the air discharge passage 32 are examples of the "oxidant gas passage" of the present disclosure.

[0028] The air supply passage 31 is provided with an air valve 40 (more specifically, an inlet side air valve 41) that opens and closes the air supply passage 31 to control the amount of air supplied to the fuel cell 11. The air valve 40 is an example of the "on-off valve" of the present disclosure.

[0029] The air discharge passage 32 is provided with an air valve 40 (more specifically, an outlet side air valve 42) that opens and closes the air discharge passage 32 to control the amount of air discharged from the fuel cell 11.

[0030] The fuel cell system 1 has a control unit 51 that controls the system. The control unit 51 performs various controls and various determinations for each device included in the fuel cell system 1. In this embodiment, the control unit 51 also controls the air valve 40.

[0031] In the fuel cell system 1 configured as described above, hydrogen gas supplied to the fuel cell 11 from the hydrogen supply passage 21 is used for power generation in the fuel cell 11, and then discharged from the fuel cell 11 to the outside of the fuel cell system 1 via the hydrogen discharge passage 22.

[0032] Furthermore, the air supplied to the fuel cell 11 through the air supply passage 31 is used for power generation in the fuel cell 11, and then discharged from the fuel cell 11 to the outside of the fuel cell system 1 through the air discharge passage 32.

[0033] <Air valve overview> Next, an overview of the air valve 40 will be described. As shown in Fig. 2, the air valve 40 has a valve section 102 configured as a double eccentric valve, a motor section 103 incorporating a motor (not shown), and a reduction mechanism section 104 incorporating a plurality of gears (not shown).

[0034] 3 and 4, the valve unit 102 includes a metal tube portion 112 having a flow path 111 through which a fluid flows, and a valve seat 113, a valve body 114, and a rotating shaft 115 are disposed within the flow path 111. The rotating force of the motor of the motor unit 103 is transmitted to the rotating shaft 115. This enables the rotating shaft 115 to rotate the valve body 114.

[0035] A step 110 is formed in the flow passage 111, and a valve seat 113 is assembled into the step 110. The valve seat 113 is annular, and has a circular or nearly circular valve hole 116 in the center. An annular seat surface 117 is formed on the edge of the valve hole 116.

[0036] In this embodiment, the valve seat 113 includes an annular rubber seal portion 113a, and this rubber seal portion 113a is formed with a seat surface 117. The rubber seal portion 113a seals the gap between the valve body 114 and the valve seat 113 when the air valve 40 is in a fully closed state. The rubber seal portion 113a is an example of the "sealing member" of the present disclosure.

[0037] The valve element 114 is disk-shaped, and on its outer periphery, an annular seal surface 118 corresponding to the seat surface 117 is formed. The valve element 114 is fixed to a rotating shaft 115, and rotates integrally with the rotating shaft 115. This causes the valve element 114 to come into contact with or move away from the valve seat 113.

[0038] As shown in Figure 6, the central axis L1 of the rotating shaft 115 extends parallel to the radial direction of the valve body 114 and the valve hole 116 and is positioned eccentrically from the central axis P1 of the valve hole 116 in the radial direction of the valve hole 116, and the sealing surface 118 of the valve body 114 is positioned eccentrically from the central axis L1 of the rotating shaft 115 in the direction in which the central axis L2 of the valve body 114 extends.

[0039] The air valve 40 opens and closes by rotating the valve element 114 about the central axis L1 of the rotary shaft 15. That is, the valve element 114 is configured to be movable between a fully closed position (see FIG. 3) in which a seal surface 118 of the valve element 114 comes into surface contact with a seat surface 117 of the valve seat 113, and a fully open position (see FIG. 4) in which the seal surface 118 is most distant from the seat surface 117, over the entire circumferential direction of the valve seat 113 and the valve element 114.

[0040] In the air valve 40 having such a configuration, when the motor of the motor unit 103 is stopped, the opening angle of the air valve 40 is 0°, as shown in Fig. 7. Here, when the opening angle of the air valve 40 is 0°, it is referred to as a mechanical fully closed opening angle. The opening angle of the air valve 40 corresponds to the rotation angle of the rotation shaft 15.

[0041] At this mechanical fully closed opening degree, the air valve 40 is in a fully closed state (i.e., the valve body 114 is in contact with the rubber seal portion 113a of the valve seat 113 over the entire circumference) as shown in Fig. 3. In this fully closed state at the mechanical fully closed opening degree, the gap between the valve seat 113 and the valve body 114 is sealed by the rubber seal portion 113a, and the opening area between the valve seat 113 and the valve body 114 is zero as shown in Fig. 7.

[0042] Then, from this fully closed state of the mechanical fully closed opening degree, when the motor of the motor unit 103 is driven and the rotary shaft 115 rotates slightly about the central axis L1, causing the valve body 114 to rotate slightly, the opening degree of the air valve 40 becomes between 0 and α, as shown in Fig. 7. Here, when the opening degree of the air valve 40 is between 0 and α, it is referred to as the controlled fully closed opening degree.

[0043] Even at this controlled fully closed opening degree, since rubber seal portion 113a has elasticity, valve element 114 is in contact with rubber seal portion 113a of valve seat 113 over the entire circumference, and air valve 40 is in a fully closed state. Even in the fully closed state at this controlled fully closed opening degree, the gap between valve seat 113 and valve element 114 is sealed by rubber seal portion 113a, and the opening area between valve seat 113 and valve element 114 is zero, as shown in FIG.

[0044] <Methods for maintaining the sealing function of the air valve> Next, a means for maintaining the sealing function of the air valve 40 will be described.

[0045] [First embodiment] First, the first embodiment will be described.

[0046] In this embodiment, as shown in FIG. 8, when power generation by the fuel cell 11 is stopped, the control unit 51 performs a power generation stop full closure control to bring the air valve 40 into a fully closed state in order to prevent air from entering the fuel cell 11 from the air supply passage 31 or the air discharge passage 32.

[0047] Here, when performing power generation stop full-close control, if the opening degree of the air valve 40 is suddenly changed to the mechanical full-close opening degree, the load acting on the rubber seal portion 113a of the air valve 40 becomes large, and there is a risk of the rubber seal portion 113a becoming worn, particularly when the air valve 40 is used under an operating pattern in which the start and stop of power generation is frequently repeated in the fuel cell 11. Note that the mechanical full-close opening degree is an example of the "mechanical full-close opening degree" in this disclosure.

[0048] Therefore, in this embodiment, when performing power generation stop full-close control, the control unit 51 sets the opening degree of the air valve 40 to a controlled full-close opening degree that is greater than the mechanical full-close opening degree, which is 0°, depending on the time after power generation of the fuel cell 11 has stopped. This makes it possible to suppress wear of the rubber seal portion 113a.

[0049] 8, when power generation by the fuel cell 11 stops, the stack temperature ST, which is the temperature inside the fuel cell 11, gradually drops to the outside air temperature (i.e., the temperature in the environment in which the fuel cell 11 is placed) over time. Then, since gas pressure and temperature are proportional when the volume is constant (Gay-Lussac's law), under the condition that the internal volume of the fuel cell 11 is constant, as the stack temperature ST gradually drops, the stack pressure SP, which is the pressure inside the fuel cell 11, also gradually drops.

[0050] Therefore, the negative pressure of the stack pressure SP becomes large, which may cause air leakage at the air valve 40 and cause air to enter the fuel cell 11 through the air supply passage 31 or the air discharge passage 32. If air enters the fuel cell 11, this may cause unnecessary power generation in the fuel cell 11 and accelerate deterioration of the fuel cell 11.

[0051] Therefore, in this embodiment, when performing power generation stop full closure control, the control unit 51 first sets the opening degree of the air valve 40 to the control full closure opening degree, and then corrects the opening degree to the closing side, i.e., the mechanical full closure opening degree, depending on the elapsed time.

[0052] In this way, the control unit 51 puts the air valve 40 into a fully closed state to prevent air from entering the fuel cell 11 when the power generation of the fuel cell 11 is stopped. When the air valve 40 is put into a fully closed state in this way, the opening degree of the air valve 40 is first set to the controlled fully closed opening degree, rather than the mechanical fully closed opening degree. In this way, when the air valve 40 is put into a fully closed state, the opening degree of the air valve 40 is set to the controlled fully closed opening degree, which suppresses the load acting on the rubber seal portion 113a more than the mechanical fully closed opening degree, so that wear of the rubber seal portion 113a can be suppressed. Therefore, even when the air valve 40 is used under an operating pattern in which the start and stop of power generation in the fuel cell 11 is frequently repeated, the sealing function between the valve seat 113 and the valve body 114 of the air valve 40 can be maintained.

[0053] As a result, for example, when a fuel cell vehicle equipped with the fuel cell system 1 is used as a commercial vehicle that is stopped more frequently than other passenger vehicles such as commuter cars and is therefore more likely to have more opportunities for power generation by the fuel cell 11 to be stopped, wear on the rubber seal portion 113a can be suppressed even if there are more opportunities for the air valve 40 to be fully closed.

[0054] In addition, the control unit 51 corrects the opening degree of the air valve 40 to the mechanical fully closed opening degree side according to the elapsed time after setting the opening degree to the control fully closed opening degree. As a result, for example, as shown in Fig. 9, the opening degree of the air valve 40 is corrected to α, close0.5, close1.0, close2.0, close3.0, 0° according to the elapsed time (0 hr to 3.0 hr or more), and the surface pressure acting on the rubber seal portion 113a of the air valve 40 is gradually increased. Therefore, even if the stack pressure SP decreases with a drop in the stack temperature ST (an example of the "change" in this disclosure) after the power generation of the fuel cell 11 is stopped and the pressure inside the fuel cell 11 becomes negative, the air valve 40 can prevent air from entering the fuel cell 11 from the air supply passage 31 or the air discharge passage 32.

[0055] In this embodiment, more specifically, the control unit 51 performs control based on the flowcharts shown in Figures 10 to 12. First, the control unit 51 determines whether or not there is a stack-off request (i.e., a request to stop power generation by the fuel cell 11) (step S1).

[0056] Then, if there is a Stack-off request (step S1: YES), the control unit 51 determines whether the Stack-off flag (XStack-off) is "0" (step S2).

[0057] If the Stack-off flag is "0" (step S2: YES), the control unit 51 starts a timer that measures the time after Stack-off (Stack-offtime) (step S3). Note that the "time after Stack-off (Stack-offtime)" is the time that has elapsed since the power generation of the fuel cell 11 was stopped.

[0058] Next, the control unit 51 calculates the controlled fully closed opening degree (ta0_Stack-offdeg) of T0_Stack-offtime using the map of FIG. 13 (step S4).

[0059] Here, "Stack-offtime" means the time after Stack-off, and "T0_Stack-offtime" means the time after Stack-off when T0. Also, "Stack-offdeg" means the controlled fully-closed opening degree, and "ta0_Stack-offdeg" means the controlled fully-closed opening degree when the time after Stack-off is T0.

[0060] Next, the control unit 51 controls the inlet / outlet air valves to the controlled fully closed opening degree (ta0_Stack-offdeg) of T0_Stack-offtime (step S5). Note that the “inlet / outlet air valve” refers to the air valve 40, and includes both the inlet side air valve 41 and the outlet side air valve 42.

[0061] In this way, when power generation by the fuel cell 11 stops, the control unit 51 performs power generation stop full-close control, and at this time sets the opening degree of the air valve 40 to a control full-close opening degree (Stack-offdeg) that is greater than the mechanical full-close opening degree.

[0062] Next, the control unit 51 sets the Stack-off flag to "1" (step S6), sets Tn(i)=Tn(i-1)+1 (step S7), and determines whether or not it is Key-off (step S8).

[0063] Note that Tn(i) is the value of the time after Stack-off (Stack-offtime), which is "T0, T1, T2, T3, . . . , Tn-1, Tn" shown in Fig. 13. Also, "being in key-off state" means that the key switch of the fuel cell vehicle on which the fuel cell system 1 is mounted is in the off state.

[0064] If it is key-off (step S8: YES), the control unit 51 stores (Tn(i)_Stack-offtime) as the air valve control ECU restart time (step S9), and turns off the inlet / outlet air valve drive ECU (not shown) (step S10).

[0065] On the other hand, if it is not key-off (step S8: NO), the control unit 51 returns to step S1 and determines whether or not a stack-off request has been made (step S1).

[0066] Also, in step S2, if the Stack-off flag is “1” (step S2: NO), the control unit 51 acquires the time after Stack-off (Stack-offtime) (step S11) and determines whether (Tn(i)_Stack-offtime)>(Stack-offtime) (step S12).

[0067] If (Tn(i)_Stack-offtime)>(Stack-offtime) (step S12: YES), the control unit 51 determines whether or not it is Key-off (step S13).

[0068] Then, if the key is off (step S13: YES), the control unit 51 turns on the inlet / outlet air valve drive ECU (step S14), and calculates the controlled fully closed opening degree (tan(i)_Stack-offdeg) of Tn(i)_Stack-offtime using the map of FIG. 13 (step S15).

[0069] On the other hand, if it is not key-off (step S13: NO), the control unit 51 uses the map in FIG. 13 to calculate the controlled fully closed opening degree (tan(i)_Stack-offdeg) of Tn(i)_Stack-offtime (step S15).

[0070] Next, the control unit 51 controls the inlet / outlet air valves to the controlled fully closed opening degree (tan(i)_Stack-offdeg) of Tn(i)_Stack-offtime (step S16).

[0071] For example, the control unit 51 controls the inlet / outlet air valves to the controlled fully closed opening degree (ta1_Stack-offdeg) of T1_Stack-offtime or the controlled fully closed opening degree (ta2_Stack-offdeg) of T2_Stack-offtime. Note that (ta0_Stack-offdeg)>(ta1_Stack-offdeg)>(ta2_Stack-offdeg).

[0072] In this way, when the control unit 51 performs power generation stop full closure control, it first sets the opening degree of the air valve 40 to the control full closure opening degree, and then corrects it to the closing side, i.e., the mechanical full closure opening degree, depending on the elapsed time.

[0073] Next, the control unit 51 determines whether Tn(i) is equal to or greater than (n-1) (step S17).

[0074] Then, if Tn(i) is equal to or greater than (n-1) (step S17: YES), the control unit 51 controls the inlet / outlet air valves to the mechanically fully closed opening degree (step S18).

[0075] In this way, when performing power generation stop full-close control, the control unit 51 first sets the opening degree of the air valve 40 to the control full-close opening degree, and then, when a long time has elapsed, finally controls it to the mechanical full-close opening degree.

[0076] Next, the control unit 51 stops the Stack-off time measuring timer (step S19).

[0077] Next, if the key is off (step S20: YES), the control unit 51 turns off the inlet / outlet air valve drive ECU (step S21).

[0078] Furthermore, in step S17, if Tn(i) is less than (n-1) (step S17: NO), the control unit 51 sets Tn(i)=Tn(i-1)+1 (step S7).

[0079] Also, in step S1, if there is no Stack-off request (step S1: NO), the control unit 51 clears the time after Stack-off (Stack-offtime) to "0", sets the Stack-off flag to "0", and sets Tn(i)=0 (step S22).

[0080] Next, the control unit 51 continues the normal control and executes the control of the air valve 40 according to the operating state (step S23).

[0081] [Second embodiment] Next, a second embodiment will be described. The differences from the first embodiment will be described, and the description of the points in common with the first embodiment will be omitted.

[0082] In this embodiment, when the amount of decrease in stack pressure SP accompanying a drop in stack temperature ST (one example of the "amount of change" in the present disclosure) is less than the estimated amount (i.e., when the decrease in stack pressure SP accompanying a drop in stack temperature ST has not progressed significantly), it is determined that there is air leakage from the air valve 40 to the fuel cell 11, and the opening degree of the air valve 40 is corrected toward the mechanical fully closed opening degree.

[0083] Specifically, the control unit 51 measures and acquires the stack temperature ST and stack pressure SP every time a predetermined time has elapsed after the power generation of the fuel cell 11 has stopped. Then, if the amount of decrease in the stack pressure SP accompanying the decrease in the stack temperature ST since the previous acquisition is less than an estimated amount, the control unit 51 determines that a leak has occurred in the air valve 40. Then, the control unit 51 corrects the opening degree of the air valve 40 to the closing side, i.e., to the mechanically fully closed opening degree side, relative to a reference opening degree defined according to the elapsed time.

[0084] The "estimated amount" is the amount of decrease in stack pressure SP that is estimated when the stack pressure SP decreases from the previously acquired stack temperature ST to the currently acquired stack temperature ST.

[0085] That is, in this embodiment, if there is a deviation from Boyle-Charles' law, it is determined that a leak has occurred in the air valve 40. That is, for example, the internal volume of the fuel cell 11 is V (constant), the stack temperature ST immediately after the air valve 40 is fully closed is ST0, and the stack pressure SP immediately after the air valve 40 is fully closed is SP0. Also, the stack temperature ST acquired for the first time after the air valve 40 is fully closed is ST1, the stack pressure SP estimated from Boyle-Charles' law when the stack temperature ST becomes ST1 is SP1, and the stack pressure SP acquired for the first time after the air valve 40 is fully closed is sp1a. At this time, if (SP0-SP1)<(SP0-sp1a), it is determined that a leak has occurred in the air valve 40.

[0086] Moreover, the "reference opening degree defined according to the elapsed time" is, for example, a controlled fully closed opening degree (Stack-offdeg) defined according to the time after Stack-off (Stack-offtime) as shown in FIG.

[0087] In this way, when leakage from air valve 40 occurs, it is possible to detect the leakage from air valve 40 and correct the opening of air valve 40 to the mechanically fully closed opening side, thereby stopping the leakage from air valve 40. Also, since the opening of air valve 40 can be corrected according to the leakage status of air valve 40, the opening of air valve 40 can be set to an appropriate opening that does not apply excessive load to rubber seal portion 113a.

[0088] In addition, in this embodiment, when the amount of decrease in stack pressure SP accompanying a decrease in stack temperature ST matches or approximately matches the estimated amount, the control unit 51 corrects the opening degree of the air valve 40 to a standard opening degree specified according to the elapsed time.

[0089] That is, in this embodiment, if there is no deviation from Boyle's law, it is determined that there is no leakage in the air valve 40. That is, for example, if (SP0-SP1)≈(SP0-sp1a), it is determined that there is no leakage in the air valve 40.

[0090] In addition, in this embodiment, when the amount of decrease in stack pressure SP accompanying a decrease in stack temperature ST is greater than the estimated amount (i.e., when the decrease in stack pressure SP accompanying a decrease in stack temperature ST has progressed too far), the control unit 51 corrects the opening degree of the air valve 40 to the open side more than the reference opening degree specified according to the elapsed time, i.e., to the opposite side of the mechanical fully closed opening degree.

[0091] In this way, air valve 40 can be kept in a fully closed state while maintaining the opening degree of air valve 40 at an appropriate opening degree that does not apply an excessive load to rubber seal portion 113a.

[0092] After the power generation of the fuel cell 11 stops, when the decrease in the stack temperature ST and the decrease in the stack pressure SP also stop, the control unit 51 does not correct the opening degree of the air valve 40 any further toward the mechanically fully closed opening degree. As a result, the opening degree of the air valve 40 does not become the mechanically fully closed opening degree, and therefore a large load is not applied to the rubber seal portion 113a of the air valve 40, and wear of the rubber seal portion 113a can be suppressed.

[0093] More specifically, in this embodiment, the control unit 51 performs control based on the flowcharts shown in Figures 14 to 16. A difference from the first embodiment is that in step S105, the control unit 51 controls the inlet / outlet air valves to the controlled fully closed opening degree (ta0_Stack-offdeg) of T0_Stack-offtime, and then retrieves and stores the current (i.e., currently acquired) stack temperature STn and the current stack pressure SPn (step S106).

[0094] Also, in step S102, if the Stack-off flag is “1” (step S102: NO), and if (Tn(i)_Stackofftime)>(Stackofftime) (step S113: YES), the control unit 51 retrieves and stores the current stack temperature STn and the current stack pressure SPn (step S116).

[0095] Next, the control unit 51 calculates an estimated stack pressure (spna), which is the stack pressure SP estimated when the current stack temperature STn is reached from the previous (i.e., last acquired) stack temperature STn-1 and the previous stack pressure SPn-1 (step S117), and calculates the pressure difference (ΔP) from the estimated value using the following formula (step S118). [Number 1] ΔP = spna-SPn

[0096] Next, the control unit 51 uses the map of FIG. 17 to determine the fully-closed opening / closing correction opening degree Δta according to the pressure difference ΔP from the estimated value (step S119), and calculates the final fully-closed opening / closing correction amount ΔTa using the following formula (step S120). [Number 2] ΔTa(i)=ΔTa(i-1)+Δta

[0097] Here, in FIG. 17, when the pressure difference ΔP from the estimated value is equal to or greater than a predetermined value +P1, this corresponds to a case where the amount of decrease in stack pressure SP due to the decrease in stack temperature ST is less than the estimated value, and the fully closed opening / closing correction opening degree Δta is set to the opening degree on the closing side (i.e., the mechanical fully closed opening degree side).

[0098] In addition, when the pressure difference ΔP from the estimated value is greater than or equal to a predetermined value -P1 and less than a predetermined value +P1, this corresponds to the case where the amount of decrease in stack pressure SP due to the decrease in stack temperature ST matches or approximately matches the estimated value, and the fully closed opening / closing correction opening degree Δta is set to 0.

[0099] In addition, if the pressure difference ΔP from the estimated value is less than a predetermined value -P1, this corresponds to the case where the amount of decrease in stack pressure SP due to the decrease in stack temperature ST is greater than the estimated value, and the fully closed opening / closing correction opening degree Δta is set to the opening side (i.e., the opening opposite to the mechanical fully closed opening degree).

[0100] Next, the control unit 51 calculates the controlled fully closed opening degree (tan(i)_Stack-offdeg) of Tn(i)_Stack-offtime using the map of FIG. 13 (step S121), and calculates the final inlet / outlet air valve control opening degree Tan using the following formula (step S122). [Number 3] Tan = tan(i) - ΔTa(i)

[0101] Next, the control unit 51 determines whether the final inlet / outlet air valve control opening degree Tan is greater than 0 deg (that is, 0°) (step S123).

[0102] Then, if the final inlet / outlet air valve control opening degree Tan is greater than 0 deg (step S123: YES), the control unit 51 controls the inlet / outlet air valve to the control fully closed opening degree (Tan(i)_Stack-offdeg) of Tn(i)_Stack-offtime (step S124).

[0103] On the other hand, if the final inlet / outlet air valve control opening degree Tan is 0 deg (step S123: NO), the control unit 51 controls the inlet / outlet air valve to the mechanically fully closed opening degree (step S126).

[0104] [Third embodiment] Next, a third embodiment will be described. The differences from the first and second embodiments will be described, and a description of the commonalities with the first and second embodiments will be omitted.

[0105] In this embodiment, if the amount of decrease in stack pressure SP accompanying a decrease in stack temperature ST is extremely less than the estimated amount (i.e., if the decrease in stack pressure SP accompanying a decrease in stack temperature ST has hardly progressed at all), it is determined that there is an abnormality in the sealing function of the rubber seal portion 113a of the air valve 40, and a warning is issued.

[0106] Specifically, if the amount of decrease in stack pressure SP accompanying a decrease in stack temperature ST after power generation by the fuel cell 11 has stopped is less than the estimated amount by a predetermined amount or more, the control unit 51 determines that there is an abnormality in the sealing function of the rubber seal portion 113a of the air valve 40, and issues a warning, such as by turning on a malfunction warning light (MIL).

[0107] This makes it possible to detect an abnormality in the sealing function of rubber seal portion 113a due to wear of rubber seal portion 113a, and therefore to take measures to quickly restore the sealing function of rubber seal portion 113a.

[0108] In this embodiment, more specifically, the control unit 51 performs control based on the flowchart shown in Fig. 18. Note that Fig. 18 shows only a part of the process of the flowchart, and other processes of the flowchart are omitted because they are common to the processes of the flowcharts of Figs. 14 to 16.

[0109] As shown in FIG. 18, if the absolute value of the pressure difference from the estimated value (|ΔP|) is equal to or greater than a predetermined value A (step S219: NO) and the air valve temporary abnormality flag (X air valve temporary abnormality) is "1" (step S229: NO), the control unit 51 performs an air valve seal failure determination, turns on the malfunction warning light (MIL), and sets the air valve malfunction flag (X air valve malfunction) to "1" (step S232).

[0110] If the absolute value of the pressure difference from the estimated value (|ΔP|) is less than the predetermined value A (step S219: YES), the control unit 51 uses the map of FIG. 17 to determine the fully-closed opening / closing correction opening degree Δta according to the pressure difference from the estimated value (ΔP) (step S220).

[0111] Furthermore, if the absolute value of the pressure difference from the estimated value (|ΔP|) is equal to or greater than a predetermined value A (step S219: NO) and the air valve temporary abnormality flag is "0" (step S229: YES), the control unit 51 performs an air valve seal temporary abnormality determination, sets the air valve temporary abnormality flag (X air valve temporary abnormality) to "1" (step S230), and additionally corrects the fully-closed correction opening (Δta) according to the pressure difference from the estimated value (ΔP) using the map in Fig. 17 and the following formula (step S231). Note that B is the predetermined opening. [Number 4] Δta←Δta+B

[0112] [Fourth embodiment] Next, a fourth embodiment will be described. The differences from the first to third embodiments will be described, and a description of the commonalities with the first to third embodiments will be omitted.

[0113] In this embodiment, the correction history of the opening degree of the air valve 40 in the current power generation stop full closure control is stored, and the next power generation stop full closure control is performed based on this stored correction history of the opening degree of the air valve 40.

[0114] Specifically, the control unit 51 updates the reference opening defined according to the elapsed time (i.e., for example, the controlled fully closed opening (Stack-offdeg) defined according to the time after Stack-off (Stack-offtime) as shown in FIG. 13) based on the correction history of the opening of the air valve 40 when the current power generation stop fully closed control was performed. Then, when the control unit 51 performs the next power generation stop fully closed control, it corrects the opening of the air valve 40 based on the updated reference opening.

[0115] This allows the opening degree of the air valve 40 to be appropriately corrected according to the elapsed time.

[0116] In this embodiment, more specifically, the control unit 51 performs control based on the flowchart shown in Fig. 19. Note that Fig. 19 shows only a part of the process of the flowchart, and other processes of the flowchart are omitted because they are common to the processes of the flowcharts of Figs. 14 to 16.

[0117] As shown in FIG. 19, after the control unit 51 controls the inlet / outlet air valves to the mechanical fully closed opening degree (step S326), it calculates and updates the controlled fully closed opening degree (tan_Stack-offdeg) of the inlet / outlet air valves for the time after the next Stack-off as shown in the following formula, and stores it (step S327). [Number 5] ta0(i)←ta0(i-1)-Δta(i) ta1(i)←ta1(i-1)-Δta(i) ta2(i)←ta2(i-1)-Δta(i) ... tan(i)←tan(i-1)-Δta(i)

[0118] [Fifth embodiment] Next, a fifth embodiment will be described. The differences from the first to fourth embodiments will be described, and a description of the commonalities with the first to fourth embodiments will be omitted.

[0119] The control unit 51 acquires the stack temperature ST and the stack pressure SP every time a predetermined time elapses, but in this embodiment, the length of this predetermined time is adjusted according to the difference between the stack temperature ST and the outside air temperature tha.

[0120] Specifically, the greater the difference between the stack temperature ST and the outside air temperature tha, the shorter the time interval for the control unit 51 to acquire the stack temperature ST and the stack pressure ST. For example, as shown in Fig. 24, the greater the absolute temperature difference (|Δt|) between the stack temperature ST and the outside air temperature tha, the greater the amount of decrease in the stack pressure SP accompanying the decrease in the stack temperature ST, so the time interval for acquiring the stack temperature ST and the stack pressure SP is shortened.

[0121] This allows the opening degree of the air valve 40 to be controlled to an opening degree corresponding to the change in stack pressure SP which changes according to the difference between the stack temperature ST and the outside air temperature tha. That is, the greater the difference between the stack temperature ST and the outside air temperature tha, the greater the amount of decrease in stack pressure SP accompanying the decrease in stack temperature ST, but by shortening the time interval between acquiring the stack temperature ST and the stack pressure ST, the opening degree of the air valve 40 can be controlled to an appropriate opening degree corresponding to the speed of decrease in stack pressure SP.

[0122] In this embodiment, more specifically, the control unit 51 performs control based on a flowchart shown in Fig. 20. As shown in Fig. 20, first, the control unit 51 determines whether or not a Stack-off request has been made (step S401).

[0123] If there is a stack-off request (step S401: YES), the control unit 51 determines whether the stack-off flag is "0" (step S402).

[0124] Then, if the Stack-off flag is “0” (step S402: YES), the control unit 51 acquires and stores the stack temperature ST and the outside air temperature tha (step S403), and calculates the absolute temperature difference (|Δt|) between the stack temperature ST and the outside air temperature tha using the following formula (step S404). [Number 6] |Δt|=ST-tha

[0125] Next, the control unit 51 determines whether the absolute temperature difference (|Δt|) is equal to or greater than a predetermined temperature C (step S405).

[0126] If the absolute temperature difference (|Δt|) is equal to or greater than the predetermined temperature C (step S405: YES), the control unit 51 determines whether the absolute temperature difference (|Δt|) is equal to or greater than the predetermined temperature D (step S406). Note that the predetermined temperature D is higher than the predetermined temperature C.

[0127] Then, if the absolute temperature difference (|Δt|) is equal to or greater than a predetermined temperature D (step S406: YES), the control unit 51 sets the time interval for acquiring the stack temperature ST and the stack pressure ST to "small" (step S407), and calculates the controlled fully closed opening degree (Steak-offdeg) using the map of pattern (1) shown in FIG. 21 (step S408).

[0128] On the other hand, if the absolute temperature difference (|Δt|) is less than the predetermined temperature D (step S406: NO), the control unit 51 sets the time interval for acquiring the stack temperature ST and the stack pressure ST to "medium" (step S409), and calculates the controlled fully closed opening degree (Steak-offdeg) using the map of pattern (2) shown in FIG. 22 (step S410).

[0129] Furthermore, in step S405, if the absolute temperature difference (|Δt|) is less than the predetermined temperature C (step S405: NO), the control unit 51 sets the time interval for acquiring the stack temperature ST and the stack pressure ST to "large" (step S411), and calculates the controlled fully closed opening degree (Steak-offdeg) using the map of pattern (3) shown in FIG. 23 (step S412).

[0130] Also, in step S402, if the Stack-off flag is “1” (step S402: NO), the control unit 51 calculates the control fully closed opening degree (Steak-offdeg) using a map of judgment pattern X (not shown), and continues the control (step S413).

[0131] Furthermore, in step S401, if there is no stack-off request (step S401: NO), the control unit 51 continues normal control and executes control of the air valve 40 according to the operating state (step S414).

[0132] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way. Needless to say, various improvements and modifications are possible without departing from the spirit and scope of the present disclosure.

[0133] For example, in the above explanation, the air valve 40, which is a double eccentric valve, is shown as an example of the "on-off valve" of the present disclosure, but the "on-off valve" of the present disclosure is not limited to this, and may be other valves such as a poppet valve, an eccentric butterfly valve, a butterfly valve, or a swing valve.

[0134] In the above description, the rubber seal portion 113a is provided on the valve seat 113, but this is not limiting, and the rubber seal portion may be provided on the valve body 114.

[0135] In the above explanation, air leakage at the air valve 40 is determined based on the amount of decrease in stack pressure SP accompanying a decrease in stack temperature ST after power generation by the fuel cell 11 is stopped, but air leakage at the air valve 40 may be determined based on the amount of increase in stack pressure SP (an example of the "amount of change" in the present disclosure) accompanying an increase in stack temperature ST (an example of the "change" in the present disclosure). Note that a case in which the stack temperature ST increases after power generation by the fuel cell 11 is stopped may be when a vehicle parked in an air-conditioned (cooled) garage in midsummer goes outside and is parked (stopped) under the hot sun without the stack temperature ST having risen to the outside temperature. [Explanation of symbols]

[0136] 1. Fuel cell system 11 Fuel Cell 31 Air supply passage 32 Air exhaust passage 40 Air valve 41 Inlet air valve 42 Outlet air valve 51 Control section 102 Valve section 113 Valve seat 113a Rubber seal part 114 Valve body ST Stack Temperature SP Stack Pressure Stack-offtime Time after Stack-off Stack-off degree control spna estimated stack pressure ΔP Pressure difference from estimated value tha Outside temperature |Δt| Absolute temperature difference

Claims

1. A fuel cell; an oxidant gas passage connected to the fuel cell and through which an oxidant gas flows; an on-off valve that opens and closes the oxidant gas passage; A control unit that performs various controls; In a fuel cell system having The on-off valve is A valve seat; A valve body that abuts against or moves away from the valve seat; a seal member provided on either the valve seat or the valve body, for sealing a gap between the valve body and the valve seat when the on-off valve is in a fully closed state; The control unit is When power generation by the fuel cell is stopped, a power generation stop full closure control is performed to bring the on-off valve into a full closure state; when performing the power generation stop full-close control, the opening degree of the on-off valve is set to a control full-close opening degree which is larger than the mechanical full-close opening degree which is 0°, and thereafter, the control full-close opening degree is corrected according to the elapsed time; A fuel cell system comprising:

2. 2. The fuel cell system of claim 1, The control unit is After the power generation of the fuel cell is stopped, acquiring a temperature of the fuel cell and an internal pressure of the fuel cell every time a predetermined time has elapsed; when an amount of change in the internal pressure of the fuel cell associated with a change in the temperature of the fuel cell since the previous acquisition is less than an estimated amount, it is determined that a leak has occurred in the on-off valve, and the opening degree of the on-off valve is corrected to the mechanical full-close opening degree side from a reference opening degree defined according to the elapsed time; A fuel cell system comprising:

3. 3. The fuel cell system according to claim 2, the control unit determines that there is an abnormality in the sealing function of the seal member and issues a warning when the amount of change in the internal pressure of the fuel cell is less than the estimated amount by a predetermined amount or more; A fuel cell system comprising:

4. 2. The fuel cell system of claim 1, The control unit is After the power generation of the fuel cell is stopped, acquiring a temperature of the fuel cell and an internal pressure of the fuel cell every time a predetermined time has elapsed; when an amount of change in the internal pressure of the fuel cell associated with a change in the temperature of the fuel cell since the previous measurement coincides or substantially coincides with an estimated amount, correcting the opening degree of the on-off valve to a reference opening degree that is defined in accordance with the elapsed time; A fuel cell system comprising:

5. 2. The fuel cell system of claim 1, The control unit is After the power generation of the fuel cell is stopped, acquiring a temperature of the fuel cell and an internal pressure of the fuel cell every time a predetermined time has elapsed; when an amount of change in the internal pressure of the fuel cell associated with a change in the temperature of the fuel cell since the previous acquisition is greater than an estimated amount, correcting the opening degree of the on-off valve to the opposite side of the mechanical fully closed opening degree from a reference opening degree defined according to the elapsed time; A fuel cell system comprising:

6. 6. The fuel cell system according to claim 1, The control unit is the opening degree of the on-off valve is corrected based on a reference opening degree defined according to the elapsed time, updating the reference opening degree based on a correction history of the opening degree of the on-off valve when the current power generation stop full closure control was performed; when performing the power generation stop full closure control next time, the opening degree of the on-off valve is corrected based on the updated reference opening degree; A fuel cell system comprising:

7. 6. The fuel cell system according to claim 2, the control unit adjusts the length of the predetermined time period in accordance with a difference between a temperature of the fuel cell and an outside air temperature; A fuel cell system comprising:

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