Fuel cell system and control methods for it

Abstract

Fuel cell system (3), comprising: a fuel cell (20); an on / off valve (46) which is configured to be able to reduce the pressure of a fuel gas, wherein the on / off valve (46) regulates a quantity state of the fuel gas supplied to the fuel cell (20); a fuel gas supply channel (42) with a first channel (42C) extending between the fuel cell (20) and the on / off valve (46), and a second channel extending from the on / off valve (46) via a shut-off valve (44) to a fuel gas supply source (41); a first pressure sensor (P1) that detects the pressure of the fuel gas in the first channel (42C); has a second pressure sensor (P3, P4) that detects the pressure of the fuel gas in the second channel; a circulation channel (43) that returns fuel exhaust gas that has been discharged from the fuel cell (20) to the first channel (42C); a drain valve (72) for draining a liquid from the circulation channel (43) in the circulation channel (43); and a controller (60) connected to the on / off valve (46), the shut-off valve (44), the first pressure sensor (P1) and the drain valve (72), characterized in that the fuel cell system (3) further comprises a gas outlet mechanism (49) that releases the fuel gas in the first channel (42C) from the first channel (42C) when the pressure of the fuel gas in the first channel (42C) exceeds a threshold value, wherein: If a pressure value detected by the first pressure sensor (P1) is abnormal, the controller (60) closes the shut-off valve (44) and the drain valve (72); and Then, if the pressure value detected by the first pressure sensor (P1) has decreased, the controller (60) determines that the on / off valve (46) has failed, whereas if the pressure value detected by the first pressure sensor (P1) has not decreased, the controller (60) determines that the first pressure sensor (P1) has failed, wherein: the controller (60) stops the power generation of the fuel cell (20) after it has closed the shut-off valve (44) and before it determines whether the pressure value detected by the first pressure sensor (P1) has decreased; the controller (60), after closing the shut-off valve (44), causes the second pressure sensor (P3, P4) to monitor a pressure reduction in the second channel; and, As a result of the monitoring, if a pressure reduction is observed in the second channel, the controller (60) determines whether the pressure value detected by the first pressure sensor (P1) has decreased, whereas if a pressure reduction is not observed in the second channel, the controller (60) determines that the first pressure sensor (P1) has failed.

Description

Background area

[0001] The present invention relates to a fuel cell system. Description of the state of the art

[0002] JP 2010-021 127 A discloses a fuel cell system in which high-pressure hydrogen from a hydrogen tank is subjected to pressure reduction by means of a pressure control valve and then supplied to a fuel cell. The supply pressure of the hydrogen delivered to the fuel cell is measured by a hydrogen pressure sensor located downstream of the pressure control valve. The hydrogen pressure sensor is driven by a voltage supplied by a constant voltage regulator. In such a fuel cell system, the power output of the fuel cell is stopped if the constant voltage regulator fails.

[0003] In another known fuel cell system, the supply pressure of hydrogen to a fuel cell is regulated by an on / off valve (an injector) (see JP 2008-071 734 A). Such a hydrogen supply pressure is also detected by a pressure sensor located downstream of the on / off valve.

[0004] For the state of the art, reference is also made to DE 11 2008 000 393 T5, which shows a fuel cell system according to the preamble of claim 1, and to JP 2008- 112 702 A.

[0005] If a specific failure occurs, it is likely that the aforementioned pressure sensors will register a pressure value much higher than the supply pressure of the hydrogen delivered to the fuel cell. However, conventional configurations have not considered whether such a pressure increase results from a pressure sensor failure or from other factors (e.g., an abnormal supply of hydrogen gas), and therefore there is still room for improvement. Summary

[0006] An object of the present invention is to provide a fuel cell system capable of determining when a pressure sensor, arranged downstream of an on / off valve, detects an abnormal pressure value and the cause of the abnormal value, and to implement suitable fail-safe operation, as well as to provide a control method for such a fuel cell system. This object is achieved with the fuel cell system according to claim 1 and the control method according to claim 11; advantageous embodiments are the subject of the dependent claims.

[0007] One embodiment provides a fuel cell system comprising: a fuel cell; an on / off valve configured to reduce the pressure of a fuel gas, the on / off valve regulating the quantity of fuel gas supplied to the fuel cell; a fuel gas supply channel with a first channel extending between the fuel cell and the on / off valve, and a second channel extending from the on / off valve through a shut-off valve to a fuel gas supply source; a first pressure sensor sensing the fuel gas pressure in the first channel; a gas outlet mechanism that releases the fuel gas from the first channel when the fuel gas pressure in the first channel exceeds a threshold; and a recirculation channel that returns fuel exhaust gas discharged from the fuel cell to the first channel.A drain valve for draining a liquid from the circulation channel; and a controller connected to the on / off valve, the shut-off valve, the first pressure sensor, and the drain valve. The controller closes the shut-off valve and the drain valve when a pressure reading detected by the first pressure sensor is abnormal; and the controller then determines that the on / off valve has failed if the pressure reading detected by the first pressure sensor has decreased, whereas the controller determines that the first pressure sensor has failed if the pressure reading detected by the first pressure sensor has not decreased.

[0008] One embodiment provides a control method for a fuel cell system. The fuel cell system comprises a fuel cell; an on / off valve configured to reduce the pressure of a fuel gas, the on / off valve regulating the quantity of fuel gas supplied to the fuel cell; a fuel gas supply channel, comprising a first channel extending between the fuel cell and the on / off valve, and a second channel extending from the on / off valve through a shut-off valve to a fuel gas supply source; a first pressure sensor sensing the pressure of the fuel gas in the first channel; and a gas outlet mechanism that releases the fuel gas from the first channel when the pressure of the fuel gas in the first channel exceeds a threshold value.A circulation channel that returns fuel exhaust gas, drained from the fuel cell, to the first channel; a drain valve for draining any liquid in the circulation channel; and a controller connected to the on / off valve, the shut-off valve, the first pressure sensor, and the drain valve. The method comprises: determining, by the controller, that a first pressure reading detected by the first pressure sensor is an abnormal value; closing, by the controller, the shut-off valve and the drain valve; and determining, by the controller, that the on / off valve has failed if a second pressure reading detected by the first pressure sensor is lower than the first pressure reading, whereas the controller determines that the first pressure sensor has failed if the second pressure reading is not lower than the first pressure reading.

[0009] According to such embodiments, the shut-off valve closes when the pressure reading detected by the first pressure sensor downstream of the on / off valve is abnormal. Consequently, the fuel gas supply from the fuel gas supply source to the fuel cell is stopped. The drain valve is also closed. Therefore, a closed space is defined downstream of the shut-off valve. Specifically, if the on / off valve is not affected by a closing failure (where the on / off valve is no longer able to close), a closed space is defined by the first channel, the fuel cell, and the circulation channel. If the on / off valve is affected by a closing failure, a closed space is defined by: a channel between the shut-off valve and the on / off valve in the second channel; in addition to the first channel, the fuel cell, and the circulation channel.If the on / off valve is affected by a closing failure, the fuel gas in the first channel is released by the gas outlet mechanism, even though the pressure in the first channel is increased. Consequently, the overall pressure in the enclosed space containing the first channel is reduced. When the pressure in the first channel is reduced to a threshold value of the gas outlet mechanism, the release of fuel gas by the gas outlet mechanism stops, and the fuel gas pressure detected by the first pressure sensor is lowered. In such a case, the controller determines that the on / off valve has failed. Conversely, if the on / off valve is not affected by a closing failure, the gas outlet mechanism does not release the fuel gas, and the pressure in the enclosed space is not reduced. Accordingly, the fuel gas pressure detected by the first pressure sensor is not lowered.In such a case, the controller determines that the first pressure sensor has failed. As described above, it is possible to implement a suitable fail-safe control for the failed component, since a determination is made as to whether the on / off valve or the pressure sensor has failed when the aforementioned abnormal condition occurs.

[0010] The controller can stop the fuel cell's power generation after closing the shut-off valve and before determining whether the pressure value detected by the first pressure sensor has decreased.

[0011] This feature halts the fuel cell's power generation while determining whether the on / off valve or the first pressure sensor has failed. This prevents pressure fluctuations of the fuel gas in the enclosed space if the on / off valve is not affected by a closing failure, thus improving the accuracy of the first pressure sensor failure detection.

[0012] The controller can maintain a suspended state of fuel cell power generation if it detects that the on / off valve has failed, whereas the controller can open the shut-off valve and restart fuel cell power generation if it detects that the first pressure sensor has failed.

[0013] This aspect allows for appropriate fail-safe control, as the operation of the fuel cell is modified according to the results of the investigation performed when the aforementioned abnormal condition occurs. In particular, it is possible to prevent the fuel cell from remaining in a suspended state of power generation in the situation where the first pressure sensor has failed.

[0014] The fuel cell system can further include a second pressure sensor which detects the pressure of the fuel gas in the second channel, wherein: after closing the shut-off valve, the controller causes the second pressure sensor to monitor for a pressure reduction in the second channel; and, as a result of the monitoring, if a pressure reduction is observed in the second channel, the controller determines whether the pressure value detected by the first pressure sensor has decreased, whereas if no pressure reduction is observed in the second channel, the controller determines that the first pressure sensor has failed.

[0015] With this aspect, if the first pressure sensor has failed in a configuration where a mechanical pressure control valve is located in the second channel, the failure of the first pressure sensor can be determined at an earlier time using the second pressure sensor.

[0016] The controller can open the drain valve after observing the pressure reduction in the second channel and before determining whether the pressure value detected by the first pressure sensor has decreased.

[0017] With this feature, if the on / off valve is affected by a closing failure, the pressure in the first channel, which has already been reduced by the gas outlet mechanism to the threshold value of the gas outlet mechanism, can be further reduced by opening the vent valve. Consequently, since the pressure in the closed space containing the fuel gas channel within the fuel cell has been reduced, the fuel cell can be protected from being subjected to high pressure during failure detection.

[0018] The fuel cell system can further include a pressure regulating valve between the on / off valve and the shut-off valve, wherein the pressure regulating valve reduces the pressure of the fuel gas, wherein: the second channel has a third channel extending from the on / off valve to the pressure regulating valve, and a fourth channel extending from the pressure regulating valve via a shut-off valve to the fuel gas supply source; and the second pressure sensor monitors a pressure reduction in the third and / or the fourth channel.

[0019] In some embodiments, the fuel cell system may further include: a pressure regulating valve between the on / off valve and the shut-off valve, wherein the pressure regulating valve reduces the pressure of the fuel gas; a third pressure sensor that detects the pressure of the fuel gas in a channel between the on / off valve and the pressure regulating valve;and a fourth pressure sensor that detects the pressure of the fuel gas in a channel between the pressure regulating valve and the shut-off valve, wherein: after closing the shut-off valve, the controller causes the third and fourth pressure sensors to monitor for a pressure reduction and, as a result of the monitoring, if a pressure reduction is observed by the third and fourth pressure sensors, the controller determines whether the pressure value detected by the first pressure sensor has decreased, whereas if no pressure reduction is observed by the third and fourth pressure sensors, the controller determines that the first pressure sensor has failed.

[0020] With this aspect, if the first pressure sensor has failed in a configuration where a mechanical valve is used as a pressure regulating valve, the failure of the first pressure sensor can be determined at an earlier time using the third and fourth pressure sensors.

[0021] In such a case, the controller can open the drain valve after the pressure reduction has been observed by the third and fourth pressure sensors, and before it has been determined whether the pressure value detected by the first pressure sensor has decreased.

[0022] This aspect can protect the fuel cell from being exposed to high pressure during failure detection, similar to the case mentioned above.

[0023] In some embodiments, the controller can limit the power output of the fuel cell after it has closed the shut-off valve and before it has determined whether the pressure value detected by the first pressure sensor has decreased.

[0024] With this aspect in mind, since the fuel cell generates electricity while its power output is limited, the fuel gas in the enclosed space is consumed. Consequently, if the on / off valve experiences a closing failure, a pressure reduction occurs in the enclosed space due to the fuel gas consumption, in addition to the pressure reduction in the enclosed space caused by the gas outlet mechanism. Therefore, if the on / off valve experiences a closing failure, the failure can be detected at an earlier time.

[0025] In such a case, the fuel cell system may further include a second pressure sensor which detects a pressure of the fuel gas in the second channel, wherein: the controller, after closing the shut-off valve, determines a power output limit value of the fuel cell based on a pressure value detected by the second pressure sensor; and the controller limits the power output of the fuel cell based on the determined power output limit value.

[0026] With this feature, the amount of fuel gas remaining in the second channel between the shut-off valve and the on / off valve can be determined from the pressure value detected by the second pressure sensor. Accordingly, the fuel cell's power generation can be maintained with a power output limit based on the remaining amount of fuel gas.

[0027] The fuel cell system may further comprise: a pressure regulating valve between the on / off valve and the shut-off valve, wherein the pressure regulating valve reduces the pressure of the fuel gas; a third pressure sensor that detects the pressure of the fuel gas in a channel between the on / off valve and the pressure regulating valve; and a fourth pressure sensor that detects the pressure of the fuel gas in a channel between the pressure regulating valve and the shut-off valve, wherein: the controller stops the power generation of the fuel cell after the pressure values ​​detected by the third and fourth pressure sensors equalize, after the power output of the fuel cell has been limited;and the controller then maintains a suspended state of fuel cell power generation if it detects that the on / off valve has failed, whereas the controller restarts fuel cell power generation by opening the shut-off valve if it detects that the first pressure sensor has failed.

[0028] This aspect, since the fuel cell's power generation is halted after the pressure values ​​detected by the third and fourth pressure sensors equalize, can increase the accuracy of the first pressure sensor's failure detection, provided the on / off valve is not affected by a closing failure. Furthermore, because the fuel cell's operation is based on the detection result, appropriate fail-safe control can be implemented.

[0029] The controller can open the drain valve after it has stopped the fuel cell generating power and before it has determined whether the pressure value detected by the first pressure sensor has decreased.

[0030] This aspect can protect the fuel cell from being subjected to high pressure during failure detection, similar to the case mentioned above.

[0031] After closing the shut-off valve, the controller can cause the fuel cell to perform normal power generation; and the controller can begin to limit the power output of the fuel cell after a pressure value detected by the fourth pressure sensor has fallen below a threshold.

[0032] This aspect allows for the further promotion of pressure reduction in the enclosed space due to the normal power generation of the fuel cell during the initial phase of such a failure, should the on / off valve be affected by a closure failure. Accordingly, if the on / off valve is affected by a closure failure, the failure can be determined at an earlier stage of the closure failure.

[0033] In some of the aforementioned aspects of the fuel cell system, the on / off valve may be an injector. The gas outlet mechanism may be a pressure relief valve connected to the first channel. The controller may close the shut-off valve before closing the vent valve if the pressure reading from the first pressure sensor is abnormal.

[0034] In some of the aspects of the fuel cell system mentioned above, the controller can determine that the pressure value is abnormal if the pressure sensor detected by the first pressure sensor exceeds a threshold.

[0035] With this aspect, it is possible to easily determine the occurrence of an abnormal pressure value detected by the first pressure sensor. Brief description of the drawings Fig. Figure 1 is a block diagram showing a configuration of a fuel cell system according to one embodiment. Fig. 2 is a flowchart that shows a first control procedure for the fuel cell system in Fig. 1 shows. Fig. Figure 3 is a flowchart showing a second control method for the fuel cell system in Fig. 1 shows. Detailed description

[0036] Preferred embodiments of the present invention are described below with reference to the accompanying drawings.

[0037] As in Fig. As shown in Figure 1, a fuel cell vehicle 1 comprises a drive motor 2 and a fuel cell system 3. The drive motor 2 can, for example, be a three-phase motor that serves as the power source for the fuel cell vehicle 1. The fuel cell system 3 can comprise a fuel cell 20, which generates electricity by means of an electrochemical reaction of hydrogen gas and oxidation gas; an oxidation gas supply system 30, which supplies air as oxidation gas to a cathode electrode of the fuel cell 20; a fuel gas supply system 40, which supplies hydrogen as fuel gas to an anode electrode of the fuel cell 20; an energy system 50, which controls the charging and discharging of electricity; and a controller 60, which collectively controls the entire system.The fuel cell 20 can be a solid polyelectrolyte fuel cell stack formed by stacking a plurality of cells, for example, in series, and the fuel cell 20 functions as a power supply in the vehicle. The fuel cell 20 has, within itself, an oxidation gas channel 21 through which the oxidation gas is supplied, and a fuel gas channel 22 through which the fuel gas is supplied.

[0038] The oxidation gas supply system 30 has an oxidation gas supply channel 31, through which oxidation gas flows to be supplied to the fuel cell 20, and an oxidation exhaust channel 32, through which oxidation exhaust gas flows to be discharged from the fuel cell 20. The oxidation gas supply channel 31 is equipped with an air compressor 34, which introduces oxidation gas from the atmosphere via a filter 33, a humidifier 35, which humidifies the oxidation gas, and a throttle valve 36, which regulates the amount of oxidation gas supplied. The oxidation exhaust channel 32 is equipped with a backpressure control valve 37 for regulating the supply pressure of the oxidation gas. The humidifier 35 humidifies the oxidation gas by means of moisture exchange between the oxidation gas (dry gas) and the oxidation exhaust gas (wet gas). The humidifier 35 can be omitted.

[0039] The fuel gas supply system 40 has a fuel gas supply source 41, a fuel gas supply channel 42 through which fuel gas supplied from the fuel gas supply source 41 flows to the fuel cell 20, and a circulation channel 43 to allow fuel exhaust gas expelled from the fuel cell 20 to return to the fuel gas supply channel 42. The fuel gas supply source 41 stores hydrogen at high pressure (e.g., 35 MPa to 70 MPa). The fuel gas supply source 41 is formed, for example, from a hydrogen tank, a hydrogen-absorbing alloy, or the like. Alternatively, the fuel gas supply source 41 can include a reformer that produces hydrogen-rich reformed gas from a hydrocarbon-based fuel, and a high-pressure gas tank that collects the reformed gas produced in the reformer after it has been brought to a high-pressure state.

[0040] The fuel gas supply channel 42 is equipped with a shut-off valve 44, a pressure control valve 45, and an injector 46. The shut-off valve 44 allows or stops the supply of fuel gas from the fuel gas supply source 41 through the fuel gas supply channel 42 to the fuel cell 20. The shut-off valve 44 acts as the main valve for the fuel gas supply source 41. The pressure control valve 45 is a pressure reducing valve that reduces the pressure on the upstream side of the pressure control valve 45 (primary pressure) to a preset secondary pressure. Although the pressure control valve 45 can use any mechanical, electrical, or electromagnetic configuration, a mechanical valve is used in the present embodiment.For example, the mechanical pressure control valve 45 has a known configuration with a housing in which a back pressure chamber and a pressure control chamber with a diaphragm are formed, the diaphragm dividing these chambers. The primary pressure is reduced to a predetermined secondary pressure in the pressure control chamber by applying back pressure in the back pressure chamber. The pressure control valve 45 is equipped with a filter 47 located upstream of it and a pressure relief valve 48 located downstream of it. The pressure relief valve 48 is normally closed and is mechanically actuated when the pressure in a line between the pressure control valve 45 and the injector 46 exceeds a predetermined level (threshold), causing the fuel gas to be expelled from the fuel gas supply channel 42.

[0041] The injector 46 is an on / off valve configured to reduce the pressure of the fuel gas and regulate the quantity of the fuel gas supplied to the fuel cell 20. The gas quantity of the fuel gas can refer to flow velocity, pressure, temperature, concentration, etc. In this embodiment, the injector 46 is configured to regulate the supply pressure and rate of the fuel gas supplied to the fuel cell 20 with high accuracy. The injector 46 can, for example, be of an electromagnetically driven type. The injector 46 comprises: a valve seat with an injection hole for injecting the fuel gas; and a valve body driven by a solenoid to open and close the injection hole.The injector 46 performs the aforementioned regulation by, for example, moving the valve body away from the valve seat at predetermined drive intervals using an electromagnetic drive force. More than one such injector 46 can be arranged in the fuel gas supply channel 42, and in this embodiment, three injectors are arranged in parallel. Each injector 46 is equipped with a filter on its upstream side and a pressure relief valve 49 on its downstream side. The pressure relief valve 49 is normally closed and is mechanically actuated when the pressure in a line between the injector 46 and the fuel cell 20 exceeds a predetermined level (threshold), causing the fuel gas to be expelled from the fuel gas supply channel 42.

[0042] The pressure of the fuel gas supplied from the fuel gas supply source 41 to the fuel cell 20 is reduced by the pressure regulating valve 45 and the injector 46. For example, the pressure of the fuel gas output from the fuel gas supply source 41, which is 35 MPa - 70 MPa, is reduced to approximately 1.5 MPa by the pressure regulating valve 45 and further reduced to 200 kPa by the injector 46. Regarding the magnitude of the fuel gas pressure at each of these two pressure reductions, the fuel gas supply channel 42 can be divided into the following channels: a high-pressure channel 42A, extending from the fuel gas supply source 41 through the shut-off valve 44 to the pressure regulating valve 45; and a medium-pressure channel 42B, extending from the pressure regulating valve 45 to the injector 46. and a low-pressure channel 42C extending from the injector 46 to the fuel cell 20.The high-pressure channel 42A, the medium-pressure channel 42B, and the low-pressure channel 42C are each equipped with a high-pressure pressure sensor P4, a medium-pressure pressure sensor P3, and a low-pressure pressure sensor P1, respectively, to detect the fuel gas pressure in the respective channels. The shut-off valve 44, the injector 46, and the pressure sensors P4, P3, and P1 are connected to the controller 60. It should be noted that the pressure detected by the high-pressure sensor P4 when the shut-off valve 44 is open reflects the fuel gas pressure in the fuel gas supply source 41.

[0043] The low-pressure channel 42C corresponds to a "first channel" in the claims set forth below. Likewise, the intermediate-pressure channel 42B corresponds to a "third channel" located downstream of a "second channel," the high-pressure channel 42A corresponds to a "fourth channel" located upstream of the "second channel," the low-pressure sensor P1 corresponds to a "first pressure sensor," the intermediate-pressure sensor P3 corresponds to a "second pressure sensor" or a "third pressure sensor," and the high-pressure sensor P4 corresponds to the "second pressure sensor" or a "fourth pressure sensor." The pressure relief valve 49, which is connected to the low-pressure channel 42C, corresponds to a "gas outlet mechanism" for releasing fuel gas from the low-pressure channel 42C when the fuel gas pressure in the low-pressure channel 42C exceeds the threshold value.

[0044] The circulation channel 43 returns the fuel exhaust gas expelled from the fuel cell 20 to the low-pressure channel 42C. The circulation channel 43 is connected to an outlet / drain channel 73 via a gas-liquid separator 71 and an outlet / drain valve 72. The gas-liquid separator 71 collects water from the fuel exhaust gas. An outlet / drain valve 72 is a drain valve for releasing a liquid located in the circulation channel 43 from the circulation channel 43. For example, the outlet / drain valve 72 is conveniently opened by a command from the controller 60 during the power generation of the fuel cell 20 in order to expel (i.e., drain) the water collected by the gas-liquid separator 71 and the fuel exhaust gas containing impurities in the circulation channel 43 to the outlet / drain channel 73.Circulation channel 43 is equipped with a pump 75 to compress the fuel exhaust gas in circulation channel 43 and then supply the compressed fuel exhaust gas to low-pressure channel 42C. The low-pressure sensor P1 is located on the injector side with respect to the junction point between circulation channel 43 and low-pressure channel 42C. It should be noted that the fuel exhaust gas discharged through the outlet / drain valve 72 and the outlet / drain channel 73 is diluted by, for example, a diluent (not shown) and then merges with the oxidation exhaust gas in the oxidation exhaust channel 32.

[0045] The energy system 50 comprises a DC / DC converter 51, a secondary battery 52, a drive inverter 53, and auxiliary machines 55. The DC / DC converter 51 has the following functions: one to increase the DC voltage supplied by the secondary battery 52 and output the resulting voltage to the drive inverter 53; and one to decrease the voltage of the DC current generated by the fuel cell 20 or the voltage of the regenerative current generated by the drive motor 2 as a result of regenerative braking, in order to charge the secondary battery 52 with the resulting current. The charging and discharging of the secondary battery 52 is controlled by these functions of the DC / DC converter 51. Furthermore, the voltage conversion control by the DC / DC converter 51 controls an operating point of the fuel cell 20 (an output voltage, an output current).The secondary battery 52 functions as: a storage source for excess electricity; a storage source for regenerative braking; or as an energy buffer provided for load changes resulting from acceleration or deceleration of the fuel cell vehicle 1. Suitable examples of the secondary battery 52 include, for example, a nickel-cadmium battery, a nickel-hydrogen battery, and a lithium secondary battery. The drive inverter 53 can, for example, be a pulse-width modulated inverter driven by pulse-width modulation, and the drive inverter 53 converts a DC voltage output by the fuel cell 20 or the secondary battery 52 into an AC voltage according to a control command from the controller 60 and controls a torque of the drive motor 2.The auxiliary machines 55 refer collectively to various types of motors located in respective parts of the fuel cell vehicle 1 (e.g., power sources for the pumps), inverters for driving such motors, and various types of auxiliary machines in the vehicle (e.g., air compressor, injector, coolant circulation pump, radiator, etc.).

[0046] The controller 60 is an electronic control unit comprising a CPU 61, a memory 62, and an input / output interface 63. The controller 60 can, for example, be configured as a microcomputer. The CPU 61 performs a desired operation according to a control program and executes various types of processes and controls. The memory 62 has, for example, ROM and RAM. The ROM stores control programs and control data processed by the CPU 61, and the RAM is used for various work areas, primarily for control processing. The input / output interface 63 is connected to devices that form parts of the fuel cell vehicle 1, such as the air compressor 34, the pressure sensors P1, P3, and P4, the shut-off valve 44, the injector 46, the DC-DC converter 51, the drive inverter 53, the outlet / drain valve 72, and the pump 75.With such a configuration, the controller 60, upon receiving an input signal from various sensor types, such as the pressure sensors P1, P3, and P4, sends a command signal to various types of consumers in order to control the entire system of the fuel cell vehicle 1. For example, the controller 60 controls the DC-DC converter 51 to regulate the output voltage of the fuel cell 20, thereby controlling the operating point (one output voltage, one output current) of the fuel cell 20.

[0047] Should a closing failure of injector 46 occur (a phenomenon in which the valve body of injector 46 becomes unable to fully close the injection hole of the valve seat, for example, due to clumping of foreign matter, a short circuit in a power source, etc.) during operation of the fuel cell system 3, the fuel gas flows to the downstream side without its pressure being reduced by injector 46, causing the pressure on the downstream side of injector 46 to rise. As a result, pressure sensor P1 detects an abnormal upper limit (a higher value than the series of pressures detected by pressure sensor P1 during normal operation). Conversely, if pressure sensor P1 fails (e.g., due to drift), it may also detect an abnormal upper limit.Accordingly, if the pressure sensor P1 detects the abnormal upper limit, it is impossible to determine, based solely on the detected value, whether the pressure sensor P1 or the injector 46 has failed. In light of such circumstances, the controller 60 of the present embodiment is configured to execute a predefined sequence of actions when the aforementioned abnormal upper limit is detected, in order to determine whether the pressure sensor P1 or the injector 46 has failed.

[0048] The following description outlines a sequence of actions that are carried out when pressure sensor P1 detects an abnormal value, with respect to Fig. 2. Each process in the sequence control is carried out by controller 60.

[0049] During normal operation of the fuel cell system 3, the pressure of the fuel gas supplied from the fuel gas supply source 41 to the fuel cell 20 is monitored by the pressure sensors P4, P3, and P1. During this time, pressure sensor P4 detects a pressure in the fuel gas supply source 41 (e.g., 35 MPa - 70 MPa), pressure sensor P3 detects a pressure reduced by the pressure control valve 45 to, for example, approximately 1.5 MPa, and pressure sensor P1 detects a pressure reduced by the injector 46 to, for example, approximately 200 kPa. In this context, pressure sensors P4, P3, and P1 are defined as being in a normal state as long as they indicate pressure values ​​within, for example, the following ranges: Pressure sensor P4: 1-70 MPa; Pressure sensor P3: 1.2 - 1.6 MPa; and Pressure sensor P1: 0-300 kPa

[0050] Under such conditions, the specified pressures at which pressure relief valves 48, 49 are mechanically activated (relief pressures) are set to the following values: Pressure relief valve 48: 2 MPa; and Pressure relief valve 49: 350 kPa

[0051] Based on a pressure reading from pressure sensor P1 (step S10), controller 60 determines whether or not an abnormal pressure is present in the low-pressure channel 42C. Specifically, if the pressure reading from pressure sensor P1 exceeds a threshold, controller 60 determines that this pressure reading is abnormal (step S10: Yes). Here, the threshold is set to an upper limit (300 kPa) of the range of values ​​recorded by pressure sensor P1 under normal conditions. However, the threshold is set to a lower limit (1.2 MPa) of the range of normally recorded values ​​from pressure sensor P3. Alternatively, the threshold can be set to the relief pressure of pressure relief valve 49 or higher. If controller 60 determines that an abnormal pressure has occurred in the low-pressure channel 42C, it closes shut-off valve 44 (step S11).Consequently, the supply of fuel gas from the fuel gas supply source 41 to the fuel gas supply channel 42 is stopped. The control device 60 can cause an alarm light of the fuel cell vehicle 1 to illuminate and simultaneously close the shut-off valve 44.

[0052] Next, the controller 60 obtains pressure values ​​detected by pressure sensors P3 and P4 (step S12). Based on these pressure values, the controller 60 calculates the amount of fuel gas remaining in the lines. Specifically, it calculates the amount of fuel gas remaining in the high-pressure channel 42A between the shut-off valve 44 and the pressure regulating valve 45, based on the pressure value detected by pressure sensor P4, and calculates the amount of fuel gas remaining in the medium-pressure channel 42B, based on the pressure value detected by pressure sensor P3. These calculations allow the controller to determine the total amount of fuel gas remaining in the lines upstream of the injector 46.

[0053] The controller 60 then stops the power generation of the fuel cell 20 and closes the outlet / drain valve 72 (step S13). Specifically, the operating mode of the fuel cell 20 is switched to intermittent operation, and the discharge of liquid from the outlet / drain valve 72 is stopped. Consequently, if the injector 46 is not affected by a closure failure, a closed space is defined by the low-pressure channel 42C, the fuel gas channel 22, and the circulation channel 43. If, on the other hand, the injector 46 is affected by a closure failure, a closed space is defined by a channel between the shut-off valve 44 and the pressure control valve 45 in the high-pressure channel 42A and the medium-pressure channel 42B, in addition to the aforementioned low-pressure channel 42C, the fuel gas channel 22, and the circulation channel 43.

[0054] The controller 60 then waits until a certain period of time has elapsed while it instructs pressure sensors P1, P3, and P4 to monitor their relevant pressures (step S14). During this waiting period, if the injector 46 is not affected by a closing failure, the fuel gas is not vented from the pressure relief valve 49, and the pressure in the aforementioned space is therefore not reduced. Accordingly, the pressure values ​​recorded by pressure sensors P4 and P3 during and after the waiting period should not differ from the pressure values ​​recorded in step S12.Given this, the controller 60 determines, in situations where, after a certain time period has elapsed (step S14), the pressure value detected by pressure sensor P4 has not decreased (step S15: No) or the pressure value detected by pressure sensor P3 has not decreased (step S16: No), that pressure sensor P1 has failed (in an abnormal state) (step S21). In this way, by defining the enclosed space and using pressure sensors P4 and P3, if pressure sensor P1 has failed, such a failure can be determined at an earlier time.

[0055] If, however, injector 46 experiences a closing failure during the waiting period (step S14), the pressure in the low-pressure channel 42C is increased first. If this increased pressure exceeds the relief pressure of the pressure relief valve 49, the fuel gas is released from the pressure relief valve 49. As a consequence of this fuel gas release, the pressure in the high-pressure channel 42A is reduced first. This is because the fuel gas remaining in the high-pressure channel 42A between the shut-off valve 44 and the pressure regulating valve 45 is forced to flow through the mechanical pressure regulating valve 45 to the medium-pressure channel 42B.Then, when the pressure in the high-pressure channel 42A is reduced to approximately the same level as the pressure in the medium-pressure channel 42B, the pressure in the high-pressure channel 42A and the pressure in the medium-pressure channel 42B are reduced in conjunction with each other, and finally reduced to the relief pressure (350 kPa) of the pressure relief valve 49, thus uniformly distributing the pressure in the enclosed space comprising the high-pressure channel 42A, the medium-pressure channel 42B, and the low-pressure channel 42C. That is, if the injector 46 is affected by a closing failure, the pressure values ​​detected by pressure sensors P4 and P3 should be lower after a waiting period than the pressure values ​​detected in step S12.Given this, if it is observed that both pressure values ​​detected by pressure sensors P4 and P3 have decreased (step S15: Yes and step S16: Yes), after a certain period of time has elapsed (step S14), the controller 60 determines whether the pressure value detected by pressure sensor P1 has decreased (step S18).

[0056] The "specified time interval" waited in step S14 can be set to a predetermined time interval based on trials or simulations. For example, the time required to discharge the fuel gas from the pressure relief valve 49 in the event of a closing failure in the injector 46 is determined in advance, and this time can be set as the "predetermined time interval." The "predetermined time interval" can be increased or decreased according to the calculated amount of fuel gas remaining in the lines.

[0057] Before proceeding to step S18, the controller 60 opens the outlet / drain valve 72 (step S17). Consequently, the fluid (fuel gas, fuel exhaust, and water) in the circulation channel 43 is drained into the outlet / drain channel 73, thus reducing the pressure in the enclosed space containing the fuel gas channel 22. As a result, if the injector 46 experiences a closing failure, the pressure in the fuel gas channel 22 can be reduced below the relief pressure of the pressure relief valve 49, thereby protecting the fuel cell 20 from overpressure. It should be noted that opening the outlet / drain valve 72 also allows the pressure in the enclosed space to be reduced to an upper limit of the range of values ​​detected by the pressure sensor P1 under normal conditions.

[0058] Next, the controller 60 determines whether the pressure value detected by pressure sensor P1 has decreased or not (step S18). In this context, the condition in which the pressure value detected by pressure sensor P1 has decreased indicates that the pressure value (a second pressure value) of pressure sensor P1 after closing the shut-off valve 44 is lower than the pressure value from pressure sensor P1 before closing the shut-off valve 44 (i.e., the pressure value that exceeds the threshold in step S10; a first pressure value).

[0059] If the pressure value detected by pressure sensor P1 has decreased (step S18: Yes), the controller 60 determines that injector 46 has failed (is in an abnormal state) (step S19). In this case, the controller 60 continues to halt power generation by fuel cell 20 (step S20). At this point, the controller 60 may prompt an occupant of the fuel cell vehicle 1 to check and / or replace injector 46, for example, by displaying a warning light.

[0060] If, on the other hand, the pressure value detected by pressure sensor P1 has not decreased (step S18: No), the controller 60 determines that pressure sensor P1 has failed (is in an abnormal state) (step S21). In this case, the controller 60 opens the shut-off valve 44 to restart the power generation of the fuel cell 20 (step S22). At this point, the controller 60 may prompt an occupant of the fuel cell vehicle 1 to check and / or replace pressure sensor P1, for example, by displaying a warning light. Due to the restart of power generation, the controller 60 performs control on various types of devices, such as opening the outlet / drain valve 72 as needed, which is not related to the pressure value detected by pressure sensor P1.

[0061] In the fuel cell system 3 according to the embodiment described above, the controller 60, when it detects that an abnormal pressure value has been recorded by the pressure sensor P1, closes the shut-off valve 44 and the outlet / drain valve 72 in order to define a predetermined closed space in the fuel gas supply system 40. Then, if the pressure value detected by the pressure sensor P1 has decreased, the controller 60 determines that the injector 46 has failed; conversely, if the pressure value detected by the pressure sensor P1 has not decreased, the controller 60 determines that the pressure sensor P1 has failed. Since the controller 60 determines which of the pressure sensor P1 or the injector 46 has failed when the pressure sensor P1 detects an abnormal pressure value, it is possible to implement a failsafe control suitable for the failed component.

[0062] The controller 60 stops the power generation of the fuel cell 20 after closing the shut-off valve 44 (step S11) and before determining whether the pressure value detected by the first pressure sensor P1 has decreased (step S18) (step S13). This prevents pressure fluctuations of the fuel gas in the closed space if pressure sensor P1 has failed, and therefore improves the accuracy of the failure detection of pressure sensor P1 (step S18: No).

[0063] Furthermore, after determining which of the pressure sensor P1 or injector 46 has failed, the controller 60 modifies the operation of the fuel cell 20 based on the result of this determination. Specifically, if the controller 60 determines that injector 46 has failed, it maintains the suspended state of power generation for fuel cell 20 (steps S19 and S20). However, if it determines that pressure sensor P1 has failed due to drift, etc., injector 46 regulates the fuel gas quantity to normal, and therefore the fuel cell system 3 is in a state where it can supply fuel gas to fuel cell 20 normally. Therefore, if the controller 60 determines that pressure sensor P1 has failed, it opens the shut-off valve 44 to restart power generation for fuel cell 20 (steps S21 and S22).With such a configuration, the fuel cell vehicle 1 can continue driving and therefore drive itself to a workshop.

[0064] The following description describes an alternative control sequence that is executed when pressure sensor P1 detects an abnormal value, with respect to Fig. 3. It should be noted that the following description omits features that are related to the process control from Fig. 2 common features, and only describes deviations from them.

[0065] Steps S30 to S32 are the same as steps S10 to S12 in Fig. 2. In step S32, the controller 60 calculates the total amount of fuel gas remaining in the lines upstream of the injector 46, based on the pressure values ​​detected by the pressure sensors P3 and P4, and determines a power output limit value for the fuel cell 20 based on this calculated amount (step S33). The controller 60 then closes the outlet / drain valve 72 (step S34) while maintaining normal power generation by the fuel cell 20 (step S35). During this normal power generation, the fuel gas in the aforementioned closed space is consumed by the fuel cell 20. As a result of this normal power generation, the pressure in the high-pressure channel 42A begins to decrease. If the injector 46 experiences a closing failure, the fuel gas is also discharged from the pressure relief valve 49, further reducing the pressure in the high-pressure channel 42A.

[0066] During normal power generation, pressure sensors P4 and P3 monitor the relevant pressures to ensure that fuel cell 20 does not experience a fuel gas shortage. If the pressure value detected by pressure sensor P4 falls below the threshold (step 36: Yes), controller 60 limits the power output of fuel cell 20 (step S37). The threshold should only need to be set to a value greater than the upper limit of the range of values ​​detected by pressure sensor P3 under normal conditions and can, for example, be set to 5 MPa. Controller 60 implements the power output limitation of fuel cell 20 by controlling the DC-DC converter 51 based on the power output limitation value determined in step S33.Then, when the pressure in the high-pressure channel 42A becomes equal to the pressure in the medium-pressure channel 42B (step S38: Yes), the controller 60 stops the power generation of the fuel cell 20 (step S39).

[0067] The subsequent steps S40 to S48 are the same as steps S14 to S22 in Fig. 2. For example, the controller 60 waits until a certain period of time has elapsed while it instructs pressure sensors P4, P3, and P1 to monitor their relevant pressures (step S40). During this waiting period, if the injector 46 is not affected by a closing failure, the fuel gas is not vented from the pressure relief valve 49, and therefore the pressure in the closed space encompassing the high-pressure channel 42A and the medium-pressure channel 42B should not be reduced after step S38. Given this, in situations where the pressure values ​​detected by pressure sensors P4 and P3 in step 38 remain unchanged, the controller 60 determines, after a certain period of time (step S41: No, step S42: No), that pressure sensor P1 has failed (is in an abnormal state) (step S47).If, however, injector 46 experiences a closing failure during the waiting period (step S40), the pressure in the high-pressure channel 42A and the pressure in the medium-pressure channel 42B are reduced in conjunction with each other as a result of the release of the fuel gas from the pressure relief valve 49, and are eventually reduced to the level of the pressure in the low-pressure channel 42C. Given this, if it is observed that both pressure values ​​detected by pressure sensors P4 and P3 have decreased (step S41: Yes and step S42: Yes) after a certain period of time has elapsed (step S40), the controller 60 determines whether the pressure value detected by pressure sensor P1 has decreased (step S44).

[0068] The fuel cell system 3, which includes the sequence control described above, consists of Fig. 3 determines which of the pressure sensor P1 or the injector 46 has failed if the pressure sensor P1 detects an abnormal pressure value, in the same way as in the sequence control. Fig. 2 and it is therefore possible to implement a fail-safe control suitable for the failed part.

[0069] In particular, the controller causes the fuel cell 20 to generate electricity normally for a short time (step S35) after closing the shut-off valve 44 (step S31) and before determining whether the pressure value detected by the pressure sensor P1 has decreased (step S44), and then limits the fuel cell's output power (step S37). Consequently, if the injector 46 is affected by a closing failure, a pressure reduction occurs in the enclosed space due to the consumption of the fuel gas, in addition to the pressure reduction in the enclosed space due to the pressure relief valve 49. Accordingly, the determination that the injector 46 is affected by a closing failure can be made earlier. Furthermore, the power generation of the fuel cell 20 can be restarted more quickly if the failure of the pressure sensor P1 is detected.

[0070] The embodiment described above is presented to facilitate a simple understanding of the present invention and is not intended to limit its interpretation. The elements included in the embodiment, as well as their arrangements, materials, conditions, shapes, and sizes, are not limited to those shown in the embodiment and may be modified as appropriate. For example, the pressure regulating valve 45 may be omitted. Alternatively, another pressure-reducing device (e.g., an injector) may be arranged in place of the pressure regulating valve 45. Alternatively, one or more steps (S12, part of S13, S14 to S17, S20, and S22) shown within the dashed frame in Figure 1 may be omitted. Fig. 2 are shown, or omitted in a suitable manner.

Claims

[1] Fuel cell system (3) comprising: a fuel cell (20); an on / off valve (46) which is configured to be able to reduce the pressure of a fuel gas, wherein the on / off valve (46) regulates a quantity state of the fuel gas supplied to the fuel cell (20); a fuel gas supply channel (42) with a first channel (42C) extending between the fuel cell (20) and the on / off valve (46), and a second channel extending from the on / off valve (46) via a shut-off valve (44) to a fuel gas supply source (41); a first pressure sensor (P1) that detects the pressure of the fuel gas in the first channel (42C); has a second pressure sensor (P3, P4) that detects the pressure of the fuel gas in the second channel; a circulation channel (43) that returns fuel exhaust gas that has been discharged from the fuel cell (20) to the first channel (42C); a drain valve (72) for draining a liquid from the circulation channel (43) in the circulation channel (43); and a controller (60) connected to the on / off valve (46), the shut-off valve (44), the first pressure sensor (P1) and the drain valve (72), characterized by , that the fuel cell system (3) further exhibits a gas outlet mechanism (49) that releases the fuel gas in the first channel (42C) from the first channel (42C) when the pressure of the fuel gas in the first channel (42C) exceeds a threshold value, wherein: If a pressure value detected by the first pressure sensor (P1) is abnormal, the controller (60) closes the shut-off valve (44) and the drain valve (72); and Then, if the pressure value detected by the first pressure sensor (P1) has decreased, the controller (60) determines that the on / off valve (46) has failed, whereas if the pressure value detected by the first pressure sensor (P1) has not decreased, the controller (60) determines that the first pressure sensor (P1) has failed, wherein: the controller (60) stops the power generation of the fuel cell (20) after it has closed the shut-off valve (44) and before it determines whether the pressure value detected by the first pressure sensor (P1) has decreased; the controller (60), after closing the shut-off valve (44), causes the second pressure sensor (P3, P4) to monitor a pressure reduction in the second channel; and, As a result of the monitoring, if a pressure reduction is observed in the second channel, the controller (60) determines whether the pressure value detected by the first pressure sensor (P1) has decreased, whereas if a pressure reduction is not observed in the second channel, the controller (60) determines that the first pressure sensor (P1) has failed. [2] Fuel cell system (3) according to claim 1, wherein the controller (60) opens the drain valve (72) after observing the pressure reduction in the second channel and before determining whether the pressure value detected by the first pressure sensor (P1) has decreased. [3] Fuel cell system (3) according to claim 1 or 2, further comprising a pressure regulating valve (45) between the on / off valve (46) and the shut-off valve (44), wherein the pressure regulating valve (45) reduces the pressure of the fuel gas, wherein: the second channel has a third channel (42B) extending from the on / off valve (46) to the pressure regulating valve (45), and a fourth channel (42A) extending from the pressure regulating valve (45) via a shut-off valve (44) to the fuel gas supply source (41); and The second pressure sensor (P3. P4) monitors a pressure reduction in the third and / or fourth channel (42A). [4] Fuel cell system (3) according to any one of claims 1 to 3, further comprising: a pressure regulating valve (45) between the on / off valve (46) and the shut-off valve (44), wherein the pressure regulating valve (45) reduces the pressure of the fuel gas; a third pressure sensor (P3) that detects the pressure of the fuel gas in a channel between the on / off valve (46) and the pressure regulating valve (45); and a fourth pressure sensor (P4) that detects the pressure of the fuel gas in a channel between the pressure regulating valve (45) and the shut-off valve (44), wherein: The controller (60), after closing the shut-off valve (44), causes the third pressure sensor (P3) and the fourth pressure sensor (P4) to monitor a pressure reduction, and As a result of the monitoring, if a pressure reduction is observed by the third pressure sensor (P3) and the fourth pressure sensor (P4), the controller (60) determines whether the pressure value detected by the first pressure sensor (P1) has decreased, whereas if no pressure reduction is observed by the third and fourth pressure sensors (P3, P4), the controller (60) determines that the first pressure sensor (P1) has failed. [5] Fuel cell system (3) according to claim 4, wherein the controller (60) opens the drain valve (72) after the pressure reduction has been observed by the third pressure sensor (P3) and the fourth pressure sensor (P4), and before it is determined whether the pressure value detected by the first pressure sensor (P1) has decreased. [6] Fuel cell system (3) according to any one of claims 1 to 5, wherein the controller (60) maintains a suspended state of power generation of the fuel cell (20) when it detects that the on / off valve (46) has failed, whereas the controller (60) opens the shut-off valve (44) and restarts the power generation of the fuel cell (20) when it detects that the first pressure sensor (P1) has failed. [7] Fuel cell system (3) according to any one of claims 1 to 6, wherein the on / off valve (46) is an injector. [8] Fuel cell system (3) according to any one of claims 1 to 7, wherein the gas outlet mechanism (49) is a pressure relief valve connected to the first channel (42C). [9] Fuel cell system (3) according to any one of claims 1 to 8, wherein the controller (60) closes the shut-off valve (44) before closing the drain valve (72) if the pressure value detected by the first pressure sensor (P1) is an abnormal value. [10] Fuel cell system (3) according to any one of claims 1 to 9, wherein the controller (60) determines that the pressure value is an abnormal value when the pressure sensor detected by the first pressure sensor (P1) exceeds a threshold value. [11] Control method for a fuel cell system (3), wherein the fuel cell system (3) comprises: a fuel cell (20); an on / off valve (46) configured to reduce the pressure of a fuel gas, the on / off valve (46) regulating the quantity of the fuel gas supplied to the fuel cell (20); a fuel gas supply channel (42) with a first channel extending between the fuel cell (20) and the on / off valve (46), and a second channel extending from the on / off valve (46) through a shut-off valve (44) to a fuel gas supply source (41); a first pressure sensor (P1) sensing the pressure of the fuel gas in the first channel (42C); a second pressure sensor (P3, P4) sensing the pressure of the fuel gas in the second channel;a gas outlet mechanism (49) that releases the fuel gas from the first channel (42C) when the pressure of the fuel gas in the first channel (42C) exceeds a threshold value; a circulation channel (43) that returns fuel exhaust gas that has been drained from the fuel cell (20) to the first channel (42C); a drain valve (72) for draining a liquid from the circulation channel (43); and a controller (60) that is connected to the on / off valve (46), the shut-off valve (44), the first pressure sensor (P1) and the drain valve (72), wherein the method comprises: ; Determine, by the controller (60), that a first pressure value detected by the first pressure sensor (P1) is an abnormal value; Closing, by the controller (60), the shut-off valve (44) and the drain valve (72); and Determine, by the controller (60), that the on / off valve (46) has failed if a second pressure value detected by the first pressure sensor (P1) is lower than the first pressure value, whereas determine, by the controller (60), that the first pressure sensor (P1) has failed if the second pressure value is not lower than the first pressure value, wherein, the controller (60) stops the power generation of the fuel cell (20) after it has closed the shut-off valve (44) and before it determines whether the pressure value detected by the first pressure sensor (P1) has decreased, The procedure also indicates: Causing the second pressure sensor (P3, P4), via the controller (60), to monitor a pressure reduction in the second channel after it has closed the shut-off valve (44); and As a result of the monitoring, if a pressure reduction is observed in the second channel, the controller (60) determines whether the pressure value detected by the first pressure sensor (P1) has decreased, whereas if a pressure reduction is not observed in the second channel, the controller (60) determines that the first pressure sensor (P1) has failed.

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