JP4956906B2 - Fuel cell system and hydrogen leak detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect abnormality such as leakage of hydrogen gas, component failures, or the like before starting power generation by a fuel cell. <P>SOLUTION: A control computer 400 integrates the flow rate of supplied hydrogen by a hydrogen flowmeter 300 if an opening and closing valve 200 is opened to start pressurizing the inside of a hydrogen supply passage 24. Then, it measures the pressure of hydrogen when a period for pressurization is completed to compute the flow rate of hydrogen which has flown into the hydrogen supply passage 24 from the measured pressure. The control computer 400 finds the difference between the integrated value of the flow rate measured by using the flowmeter 300 and the flow rate computed from the pressure condition to compute the leaked amount of hydrogen. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a technique for detecting leakage of hydrogen gas, component failure, and the like in a fuel cell system.

  In a fuel cell system in which hydrogen and oxygen are supplied to a fuel cell to generate power, various techniques for detecting leakage of hydrogen gas supplied to the anode of the fuel cell have been studied in order to improve safety.

  For example, Patent Document 1 describes a technique for detecting leakage of hydrogen gas based on the consumption of hydrogen gas calculated based on the output current value of the fuel cell and the supply amount of hydrogen gas measured by a flow sensor. Yes.

JP 2004-281132 A JP 2004-158274 A JP 2004-265667 A

  However, with such conventional technology, hydrogen gas consumption is calculated based on the output current value of the fuel cell, so hydrogen gas leakage is detected only while the fuel cell is actually generating power. I couldn't.

  Therefore, an object of the present invention is to detect abnormalities such as hydrogen gas leakage and component failure before power generation by a fuel cell is started.

Based on the above object, the fuel cell system of the present invention was configured as follows. That is, a fuel cell system for generating power by supplying hydrogen and oxygen to a fuel cell,
Hydrogen supply means for supplying the hydrogen to the fuel cell;
A hydrogen supply flow path connecting the hydrogen supply means and the fuel cell;
A flow rate detection means provided in the hydrogen supply flow path for detecting the flow rate of hydrogen supplied from the hydrogen supply means to the fuel cell;
State quantity detection means provided in the hydrogen supply flow path for detecting at least one of the state quantities of hydrogen supplied to the fuel cell;
A pressurization period before the start of power generation by the fuel cell and until the pressure in the hydrogen supply flow path reaches a predetermined pressure suitable for power generation of the fuel cell from the start of supply of hydrogen by the hydrogen supply means The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel cell is calculated based on the hydrogen state quantity detected by the state quantity detection unit, and the calculated flow rate and the flow rate detection unit detect A leakage detection unit that detects leakage of the hydrogen based on the flow rate ,
The gist of the leak detection unit is to detect the leak in at least a part of the period until pressurization within the pressurization period ends .

According to the fuel cell system of the present invention having such a configuration, the difference between the actual flow rate of the supplied hydrogen and the flow rate calculated based on the hydrogen state quantity is obtained, so that even before the fuel cell power generation starts. Hydrogen leakage can be detected quickly. The hydrogen state quantity is, for example, the pressure or temperature of hydrogen. In addition, with such a configuration, since the leak is detected in at least a part of the period until the pressurization within the pressurization period is completed, the occurrence of the leak can be detected in a shorter time. it can. In the fuel cell, hydrogen permeates from the anode to the cathode through the electrolyte membrane, but the permeation amount increases in proportion to the hydrogen pressure on the anode side. Therefore, if the amount of leakage is calculated in a part of the pressurization period where the pressure is as low as possible, the influence of hydrogen permeation can be suppressed to detect the leakage.

In the fuel cell system configured as described above,
The leak detection unit may detect the leak based on a change in the hydrogen state quantity in the partial period.

  With such a configuration, hydrogen leakage can be detected in a shorter time.

In the fuel cell system configured as described above,
The state quantity detection means includes means for detecting the pressure of hydrogen supplied to the fuel cell, and the leak detection unit obtains an average pressure of the hydrogen in the partial period, and in the partial period The calculated hydrogen leakage amount may be corrected to the leakage amount at the completion of the pressurization period based on the average pressure.

  By doing so, it becomes possible to accurately calculate the amount of hydrogen leakage while suppressing the influence of the cross leak of the electrolyte membrane accompanying the increase in the hydrogen pressure. In addition, by correcting the leak amount of hydrogen to the leak amount at the completion of the pressurization period, the leak reference value and the common reference value used when detecting leaks over the entire pressurization period are used. Judgment can be made.

In the fuel cell system configured as described above,
The leak detection unit may detect the leak when the pressurization period is completed.

  With such a configuration, since the flow rate can be measured over the entire pressurization period, it is possible to reduce the occurrence of errors in the calculation of the leakage amount.

In the fuel cell system configured as described above,
The hydrogen leak amount is calculated based on the calculated flow rate and the flow rate detected by the flow rate detection means at two different time points within the pressurization period, and the difference between the leak rates at the two time points is calculated. A permeation amount estimation unit that estimates the permeation amount of hydrogen permeating from the anode to the cathode through the electrolyte membrane in the fuel cell may be provided.

  With such a configuration, not only the amount of hydrogen leakage but also the amount of hydrogen cross leakage that permeates the electrolyte membrane can be estimated.

In the fuel cell system configured as described above,
The fuel cell is connected to an anode off gas flow path for discharging the anode off gas,
The anode off gas channel is connected to the hydrogen supply channel via a circulation device for circulating the anode off gas to the hydrogen supply channel,
During the pressurization period, the circulation device may be controlled to supply the hydrogen supplied from the hydrogen supply unit in a reverse flow to the anode off-gas channel.

  By supplying hydrogen back to the anode off-gas flow path with such a configuration, the hydrogen pressure in the vicinity of the fuel cell can be made uniform, so the influence of pressure loss generated by the flow path in the fuel cell. This makes it possible to accurately detect leaks. For example, an ejector or a pump can be used as the circulation device.

In the fuel cell system configured as described above,
In the hydrogen supply channel, at least one shut valve is provided between the flow rate detecting means and the fuel cell,
The state quantity detection means is provided for each section in the hydrogen supply flow path partitioned by the shut valve,
Each shut valve is closed in the initial state,
The leak detector is
Means for sequentially opening the shut valve from a shut valve provided on the flow rate detecting means side toward a shut valve provided on the fuel cell side;
The state quantity provided in a section located between the opened shut valve and an unopened shut valve or the nearest one of the fuel cells located on the fuel cell side of the opened shut valve The state quantity of the hydrogen in the section is detected by the detection means, the flow rate of hydrogen supplied from the hydrogen supply means to the section is calculated based on the state quantity, and the calculated flow rate and the flow rate are calculated. Based on the flow rate detected by the detection means, a means for detecting hydrogen leakage in the section may be provided.

  With such a configuration, it is possible to detect whether or not hydrogen leakage has occurred in each section partitioned by a shut valve or a fuel cell, so it is possible to roughly specify the location of the leakage. become.

In the fuel cell system configured as described above,
The hydrogen supply channel includes at least one pressure regulating valve;
The state quantity detection means and the flow rate detection means are provided for each section in the hydrogen supply flow path partitioned by the pressure regulating valve,
The leak detection unit may detect the leak for each section.

  With such a configuration, even in a system in which the pressure of hydrogen supplied from the hydrogen supply means is reduced stepwise by the pressure regulating valve, the section immediately before the fuel cell that has the lowest pressure is used for power generation by the fuel cell. Without waiting for a suitable pressure to be reached, hydrogen leakage can be detected when the pressure in each section reaches the pressure suitable for that section, so that hydrogen leakage can be detected quickly. Become. In addition, since leakage is detected for each section, it is possible to roughly specify the location where the leakage occurs.

In the fuel cell system having various configurations described above,
Furthermore, a pressure regulating valve for adjusting the pressure of hydrogen supplied from the hydrogen supply means is provided between the state quantity detection means and the hydrogen supply means in the hydrogen supply flow path,
The state quantity detection means comprises means for detecting the pressure of hydrogen supplied to the fuel cell,
When the leak is not detected by the leak detection means, the pressure regulating valve fails when the hydrogen pressure detected by the state quantity detection means is lower than a predetermined pressure suitable for power generation of the fuel cell. It is good also as a thing provided with the failure determination part which determines with having carried out.

  With such a configuration, it is possible to detect a failure such as a pressurization failure occurring in the pressure regulating valve even when hydrogen leakage is not detected.

In the fuel cell system configured as described above,
The fuel cell system is mounted on a vehicle, and an operation mode for setting an operation mode of the vehicle according to at least one of a leakage detection result by the leakage detection unit and a failure determination result by the failure determination unit A setting unit may be provided.

  With such a configuration, the driving mode of the vehicle can be set to the optimum mode according to the presence or absence of hydrogen leakage or failure before the start of power generation by the fuel cell.

  For example, the operation mode setting unit prohibits power generation by the fuel cell and travels by a secondary battery provided in the vehicle when the leak is detected by the leak detection unit. The allowable secondary battery operation mode may be set.

  With such a configuration, when hydrogen leakage is detected, the supply of hydrogen is stopped and power generation is prohibited, so that hydrogen can be prevented from leaking and within the range of power stored in the secondary battery. The vehicle can be driven by itself.

  In addition, when the failure determination unit determines that a failure has occurred, the operation mode setting unit sets the operation mode to a limp-form operation mode that allows traveling while limiting output to the fuel cell. It is good also as what is set to.

  With such a configuration, even if the amount of hydrogen supplied to the fuel cell decreases due to a malfunction of the pressure regulating valve, power generation is continued by limiting the output of the fuel cell, and an emergency is made to the nearest repair shop, etc. It is possible to drive the vehicle.

In addition to the configuration as the fuel cell system described above, the present invention can also be configured as the following hydrogen leak detection method. That is, in a fuel cell system for generating power by supplying hydrogen and oxygen to a fuel cell, a hydrogen leak detection method for detecting hydrogen leak,
The fuel cell system is provided in the hydrogen supply channel, a hydrogen supply unit that supplies the hydrogen to the fuel cell, a hydrogen supply channel that connects the hydrogen supply unit and the fuel cell, and the hydrogen supply channel A flow rate detection means for detecting a flow rate of hydrogen supplied from the supply means to the fuel cell; and a state in which at least one of the state quantities of hydrogen supplied to the fuel cell is provided in the hydrogen supply flow path A quantity detecting means,
A pressurization period before the start of power generation by the fuel cell and until the pressure in the hydrogen supply flow path reaches a predetermined pressure suitable for power generation of the fuel cell from the start of supply of hydrogen by the hydrogen supply means The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel cell is calculated based on the hydrogen state quantity detected by the state quantity detection unit, and the calculated flow rate and the flow rate detection unit detect The hydrogen leak detection method detects the hydrogen leak based on the measured flow rate.

  Even with such a leak detection method, by obtaining the difference between the actual flow rate of the supplied hydrogen and the flow rate calculated based on the hydrogen state quantity, hydrogen leaks can be detected quickly even before the start of power generation by the fuel cell. Can be detected.

Hereinafter, in order to further clarify the operations and effects of the present invention described above, embodiments of the present invention will be described based on examples in the following order.
A. First embodiment:
(A1) Overall configuration of fuel cell system:
(A2) Abnormality detection processing:
(A3) Modification of the first embodiment:
B. Second embodiment:
C. Variations:

A. First embodiment:
(A1) Overall configuration of fuel cell system:
FIG. 1 is an explanatory diagram showing the overall configuration of a fuel cell system 100 as a first embodiment of the present invention. As shown in the figure, the fuel cell system 100 of this embodiment is mounted on a vehicle 90, and generates a fuel cell 10 that generates electricity by an electrochemical reaction between hydrogen and oxygen, a hydrogen tank 20 that stores hydrogen gas, and a fuel cell 10. A blower 30 that supplies air to the battery, a secondary battery 40 that is charged by electricity generated by the fuel cell 10, a motor 50 that drives the axle 55 by the power generated by the fuel cell 10, a vehicle 90, and the fuel cell system 100 are provided. A control computer 400 for overall control is provided.

  The fuel cell 10 is a solid polymer electrolyte type fuel cell, and has a stack structure in which a plurality of unit cells (not shown) are stacked. Each single cell has a configuration in which a hydrogen electrode (hereinafter referred to as an anode) and an oxygen electrode (hereinafter referred to as a cathode) are arranged with an electrolyte membrane interposed therebetween. By supplying hydrogen gas to the anode side of each single cell and supplying air containing oxygen to the cathode side, an electrochemical reaction proceeds and an electromotive force is generated. The electric power generated in the fuel cell 10 is supplied to the secondary battery 40 and the motor 50 connected to the fuel cell 10.

  The blower 30 is a device for supplying air to the cathode of the fuel cell 10. The blower 30 is connected to the cathode of the fuel cell 10 via the air supply channel 34. The air (hereinafter referred to as cathode offgas) after being subjected to the electrochemical reaction is discharged to the outside through the cathode offgas flow path 36.

  The hydrogen tank 20 stores high-pressure hydrogen gas having a pressure of several tens of MPa. The hydrogen tank 20 is connected to the anode of the fuel cell 10 through the hydrogen supply channel 24. In the flow path of the hydrogen supply flow path 24, an on-off valve 200, a first pressure regulating valve 210, a hydrogen flow meter 300, and a second pressure regulating valve 220 are provided in order from the hydrogen tank 20. When the on-off valve 200 is opened by control by the control computer 400, hydrogen gas is supplied from the hydrogen tank 20 to the fuel cell 10 through the hydrogen supply channel 24. Note that the shut valve 250 indicated by a broken line in the drawing is used in a modified example described later, and is not used in the present embodiment.

  The high-pressure hydrogen gas supplied from the hydrogen tank 20 to the hydrogen supply passage 24 is regulated by the first pressure regulating valve 210 and is reduced to an intermediate pressure state of about 400 K to 2 MPa. The hydrogen gas thus regulated is further regulated by the second pressure regulating valve after passing through the hydrogen flow meter 300, and the pressure is reduced to a low pressure state of about 100 K to 250 KPa. The low-pressure hydrogen gas is supplied to the anode of the fuel cell 10. In the following description, the sections in the hydrogen supply flow path 24 that are in different pressure states depending on the first pressure regulating valve 210 and the second pressure regulating valve 220 are respectively shown in the high pressure part HS, the intermediate pressure part MS, and the low pressure part. This is called part LS.

  The hydrogen flow meter 300 measures the flow rate per unit time through which the hydrogen gas decompressed by the pressure regulating valve 210 flows in the hydrogen supply flow path 24. The hydrogen flow meter 300 is connected to the control computer 400 and is used when detecting the flow rate of hydrogen gas in an abnormality detection process described later.

  The high pressure section HS, the intermediate pressure section MS, and the low pressure section LS in the hydrogen supply flow path 24 are respectively provided with pressure sensors 310, 320, and 330 for measuring the pressure of hydrogen gas flowing through the sections. . Each of the pressure sensors 310 to 330 is connected to the control computer 400, and is used when detecting the pressure of each pressure part in an abnormality detection process described later.

  An anode off gas flow path 26 is connected to the anode side outlet of the fuel cell 10. A gas-liquid separator 60 is connected to the anode off gas passage 26. The anode off gas may contain moisture that permeates from the cathode side through the electrolyte membrane. The moisture is separated from the anode off gas by the gas-liquid separator 60 and discharged to the outside.

  A hydrogen circulation channel 28 and a purge valve 240 are connected to the gas-liquid separator 60. In the anode off gas, there may be a case where hydrogen gas that has not been used for power generation by the fuel cell 10 may remain in addition to moisture, and this hydrogen gas is again supplied to the hydrogen supply flow through the hydrogen circulation passage 28. By supplying to the path 24, hydrogen gas can be used efficiently. A circulation device 70 for circulating hydrogen gas is provided at a joint portion between the hydrogen supply channel 24 and the hydrogen circulation channel 28. For example, an ejector or a pump can be used as the circulation device 70.

  The purge valve 240 is periodically opened under the control of the control computer 400. This is because the anode off gas contains moisture and impurities such as nitrogen in the air that passes through the electrolyte membrane from the cathode as described above, and these are periodically discharged to the outside. Note that the control computer 400 may open the purge valve 240 by measuring the concentration of impurities in the anode off-gas or estimating the amount of power generated by the fuel cell.

  The control computer 400 includes a CPU, ROM, RAM, and input / output ports. The ROM stores a program for performing an abnormality detection process, which will be described later, and a program for controlling the operation of the vehicle 90 and the fuel cell system 100. The CPU develops these programs in the RAM and executes them. A hydrogen flow meter 300, pressure sensors 310 to 340, and the like are connected to the input / output port, and an on-off valve 200, a purge valve 240, a blower 30, an ignition switch, and the like are also connected.

(A2) Abnormality detection processing:
FIG. 2 is a flowchart of an abnormality detection process executed by the control computer 400 described above based on a program recorded in the ROM. This abnormality detection process is performed after the ignition switch is turned on by the driver and before the power generation by the fuel cell 10 is started, the hydrogen supply channel 24, the anode offgas channel 26, and the hydrogen circulation channel 28 (hereinafter collectively referred to as “ This is a process for detecting whether a hydrogen leak or component failure has occurred in the hydrogen system). As a premise of such processing, in the initial state, the on-off valve 200 and the purge valve 240 are closed, and the hydrogen system is closed.

When the abnormality detection process is executed, first, the control computer 400 measures the pressure P ₀ in the hydrogen supply flow path 24 using any of the pressure sensors 310 to 330 (step S200). The pressure P ₀ measured in this way is about atmospheric pressure. The average value of the pressure measured by each pressure sensor may be used as the pressure P ₀ in the hydrogen supply channel 24. When the pressure P ₀ is measured, the control computer 400 opens the on-off valve 200 (step S210). Then, high-pressure hydrogen gas is supplied into the hydrogen supply channel 24, and the pressure in the hydrogen supply channel 24 is increased. When pressurization is started, the control computer 400 detects the flow rate of the hydrogen gas supplied from the hydrogen tank 20 using the hydrogen flow meter 300 (step S220), and integrates the flow rate (step S230).

  Next, the control computer 400 determines whether the time elapsed from the start of pressurization in step S100 until the present time has passed the standard pressurization time tn. (Step S240). The standard pressurization time tn is a standard time from the start of hydrogen supply until the hydrogen pressure in the low pressure part LS in the hydrogen supply channel 24 reaches a pressure suitable for power generation by the fuel cell 10. The value of this standard pressurization time tn is stored in advance in the ROM. When the control computer 400 determines that the elapsed time up to the present time has not reached the standard pressurization time tn (step S240: No), the control computer 400 returns the process to step S220 and pressurizes the hydrogen supply flow path 24. Continue.

If it is determined that the elapsed time up to the present time has passed the standard pressurization time tn (step S240: Yes), the control computer 400 uses the pressure sensors 310 to 330 to set each pressure part in the hydrogen supply flow path 24. Each pressure is detected (step S250). Hereinafter, the pressure of the high pressure part HS detected here is P ₁ , the pressure of the intermediate pressure part MS is P ₂ , and the pressure of the low pressure part LS is P ₃ .

Next, the control computer 400 calculates the hydrogen gas leakage amount Q _leak based on the total flow rate of hydrogen gas accumulated in step S230 and the pressure of each pressure portion detected in step S250 (step S260). . The leak amount Q _leak can be calculated based on the following formula (1). In the following equation, V ₁ , V ₂ ... Represent the volume of each pressure part in the hydrogen supply flow path 24, and Q _flow represents the flow rate of hydrogen gas detected by the hydrogen flow meter 300. Yes. The first term on the left side of the equation (1) is a value obtained by measuring the total amount of hydrogen supplied to the hydrogen system with the hydrogen flow meter 300, and the second term is the total amount of hydrogen existing in the hydrogen system for each pressure part. It is a value calculated from the pressure.

The above formula (1) can also be expressed as the following formula (1b). When using this formula, it is assumed that a temperature sensor is provided in each pressure part. Here, z is a compression coefficient, R is a gas constant, T ₁ , T ₂ ... Are the temperatures of the pressure parts.

When the leak amount Q _leak calculated in this way exceeds a reference value (for example, zero) (step S270: leak amount> reference value), the control computer 400 determines that a hydrogen leak has occurred and opens / closes it. The valve 200 is closed (step S280). Then, power generation by the fuel cell 10 is prohibited (step S290), and the operation mode of the vehicle is set to an EV operation mode that allows only the operation by the secondary battery 40 (step S300). By doing so, it is possible to drive the vehicle to a safe place within the range of the electric power stored in the secondary battery while suppressing leakage of hydrogen. The reference value used for determining the _leak may be a predetermined amount α (> 0) in addition to zero in consideration of the calculation error of the _leak amount Q _leak .

On the other hand, when the leak amount Q _leak calculated in step S260 is equal to or less than the reference value (step S270: leak amount ≦ reference value), the control computer 400 determines that no hydrogen leak has occurred. Further, it is determined whether or not the pressure P ₂ of the low-pressure part LS has increased to a normal pressure suitable for power generation by the fuel cell (for example, 200 KPa) (step S310). As a result, when the pressure P ₂ does not reach the normal pressure (step S310: No), any component (for example, the first pressure regulating valve 210 or the second pressure regulating valve) provided in the hydrogen supply flow path 24 is used. It is determined that a pressurization failure or the like has occurred due to a failure of the pressure valve 220), and the operation mode of the vehicle is set to the limp foam operation mode (step S320). Then, the control computer 400 starts power generation by the fuel cell 10 while performing output restriction (step S330). As described above, if the pressure regulating valve or the like is set to the limp foam operation mode and the output of the fuel cell is limited, even if the amount of hydrogen supplied to the fuel cell decreases due to the malfunction of the pressure regulating valve or the like. By restricting the output of the fuel cell and continuing the power generation, the vehicle can be urgently run to the nearest repair shop or the like. Further, as described above, when the limp foam operation mode is set, hydrogen leakage does not occur, so there is no need to stop the fuel cell, and the self-run can be performed for a relatively longer distance than in the EV operation mode.

In the step S310, the in the case where the pressure P ₂ is determined to be a normal pressure (step S310: Yes), the control computer 400, when the hydrogen leak or component failure in the hydrogen supply flow path 24 does not occur to decide. Then, the operation mode is set to the normal operation mode (step S340), and power generation by the fuel cell 10 is started (step S350). When the control computer 400 finishes the abnormality detection process described above, the control computer 400 controls the operation of the vehicle 90 based on the operation mode set in steps S300, S320, and S340.

  According to the fuel cell system 100 of the first embodiment described above, abnormalities occurring in the hydrogen system, such as hydrogen leakage and component failures, can be quickly detected before the power generation by the fuel cell 10 is started. Therefore, the safety of the fuel cell system can be improved. The hydrogen supplied from the hydrogen tank 20 before the start of power generation by the fuel cell is not consumed by the fuel cell, and the supply amount appears as a change in the state quantity (pressure, temperature, etc.) in the hydrogen supply channel. For this reason, hydrogen leaks and component failures are detected in the hydrogen system during the pressurization period before the start of power generation by the fuel cell 10 by detecting hydrogen leaks and component failures using such state quantity changes. It is possible to detect an abnormal condition with high accuracy and speed. Further, in this embodiment, since hydrogen leaks and the like can be detected before the power generation of the fuel cell 10 is started, the fuel cell is once operated and stopped for detection of hydrogen leaks as in the prior art. Therefore, the durability of the fuel cell can be improved.

(A3) Modification of the first embodiment:
In the first embodiment described above, the leakage is determined after the standard pressurization time tn (see FIG. 2: step S240). However, leak detection may be performed during a part of the standard pressurization time tn. The electrolyte membrane in the fuel cell 10 has the property of permeating hydrogen gas from the anode to the cathode, but the permeation amount increases in proportion to the hydrogen pressure on the anode side. Therefore, if the amount of leakage is detected in a low pressure state from the start of pressurization to the middle of pressurization within the standard pressurization time tn, the effect of hydrogen permeation through the electrolyte membrane can be suppressed and hydrogen leak detected quickly. it can. In this case, the reference value used in the leakage determination in step S270 in FIG. 2 and the normal pressure compared with the pressure in the low pressure portion in step S310 can be set according to a part of the period.

As described above, when the leak amount Q _leak is calculated in a partial period within the standard pressurization time tn, the _leak calculated in step S260 of FIG. 2 is used by using the average pressure of hydrogen during this period. The amount can be corrected and converted into a leakage amount in a standard state. Thus, if the leakage amount is converted into the leakage amount in the standard state, the same value as in the first embodiment can be used as the reference value used in step S270 in FIG. 2 and the normal pressure used in step S310. Such conversion can be performed as follows.

For example, if a portion where leakage occurs is regarded as an orifice, the hydrogen flow rate Q passing through the orifice is generally expressed by the following equation (2). Where α is the orifice coefficient, F ₀ is the opening area, and γ is the gas density. These values are uniquely determined by the size of the leakage portion.

According to the above formula (2), the flow rate Q _{leak of} hydrogen gas passing through the leaking portion has a relationship as shown in the following formula (3).

Therefore, the corrected leak amount Q _leak2 can be obtained by the following equation (4). However, P _ave is the average pressure, P _a is the outside air pressure in a partial period in between the standard pressurization time tn, Q _leak above formula (1) or (1b) by the obtained hydrogen leakage amount, P _b is the fuel Hydrogen pressure suitable for battery power generation.

B. Second embodiment:
In the first embodiment described above, as shown in step S240 of FIG. 2, the leak amount Q _leak is calculated after the standard pressurization time tn has elapsed. Therefore, the flow rate of hydrogen can be detected over a relatively long period until the pressurization in the hydrogen supply flow path 24 is completed, and the occurrence of measurement errors can be reduced. On the other hand, the present embodiment aims to detect hydrogen leakage instantaneously from the relationship between the flow rate of hydrogen and the pressure change within a minute time within the standard pressurization time tn. The overall configuration of the fuel cell system 100 is the same as the configuration shown in FIG.

FIG. 3 is a flowchart of the abnormality detection process in the second embodiment. When executing the abnormality detection process, the control computer 400 first measures the pressure P ₀ in the hydrogen supply flow path 24 (step S400). Then, the on-off valve 200 is opened, and pressurization in the hydrogen supply flow path 24 is started (step S410).

After the start of pressurization, the control computer 400 uses the hydrogen flow meter 300 to detect the hydrogen gas flow rate Q _flow in the minute time dt (step S420). The minute time dt can be set to the minimum unit time that can be measured by the hydrogen flow meter 300, for example. Moreover, it is also possible to set a predetermined minute time such as 0.1 seconds or 0.01 seconds.

  The control computer 400 detects the pressure change amount dp in the hydrogen supply flow path 24 at the minute time dt simultaneously with the detection of the flow rate of the hydrogen gas (step S430). At the initial stage of pressurization, the first pressure regulating valve 210 and the second pressure regulating valve 220 are fully open, so that the pressure parts are in communication with each other and the pressure states are the same. Therefore, the sensor for measuring the pressure change only needs to be positioned downstream of the hydrogen flow meter 300. For example, the pressure sensor 320 of the intermediate pressure part MS may be used, or the pressure sensor 330 of the low pressure part LS may be used. It may be used.

Next, the control computer 400 calculates a hydrogen gas leakage amount Q _leak (step S440). Assuming that V ₀ and V ′ ₀ are the volume of hydrogen when converted to the standard state, and V is the volume of the hydrogen supply flow path 24 downstream of the hydrogen flow meter 300, the pressure P shown in step S430 in FIG. The state of hydrogen at the pressure P ′ can be expressed as follows.

PV = P ₀ V ₀
P′V = P ₀ V ′ ₀

Subtracting the left side and right side of the above two formulas,
ΔPV = P ₀ ΔV ₀
That is,
ΔP = (ΔV ₀ P ₀ ) / V
It becomes. Furthermore, when this equation is transformed, the flow rate Q is expressed as follows.

Therefore, if the flow rate measured by the hydrogen flow meter 300 is Q _flow , the leakage amount Q _leak can be calculated as follows.
Q _leak = Q _flow -Q

When the leak amount Q _leak calculated in this way exceeds a reference value (for example, zero) (step S450: leak amount> reference value), the control computer 400 determines that a leak has occurred and is shown in FIG. Then, the same processing as in steps S280 to S300 is performed, and the supply of hydrogen gas is stopped. On the other hand, if the leak amount Q _leak is less than or equal to the reference value (step S450: leak amount ≦ reference value), it is determined that no leak has occurred, and from the start of hydrogen gas supply in step S410 to the present It is determined whether or not the elapsed time has passed the standard pressurization time tn (step S460). As a result, when the standard pressurization time tn has elapsed (step S460: Yes), the same processing as steps S310 to S350 shown in FIG. 2 is performed.

  According to the second embodiment described above, hydrogen leakage can be detected instantaneously before the start of power generation by the fuel cell 10 and before the pressurization of the hydrogen system is completed. Therefore, when hydrogen leakage has occurred, the supply of hydrogen gas can be stopped quickly.

  The electrolyte membrane in the fuel cell 10 has the property of permeating hydrogen gas from the anode to the cathode, and the permeation amount increases in proportion to the hydrogen pressure on the anode side. Therefore, if Step S420 and Step S430 of the abnormality detection process are performed immediately after the start of pressurization of the hydrogen supply flow path 24, the influence of cross leak due to the electrolyte membrane is suppressed and hydrogen leak is detected quickly. be able to.

C. Variations:
While various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can of course be implemented in various forms without departing from the spirit of the present invention. . For example, the following modifications are possible.

(Modification 1)
In the fuel cell 10, the permeation amount of hydrogen gas that permeates from the anode side to the cathode side through the electrolyte membrane increases in proportion to the hydrogen partial pressure on the anode side. Therefore, if the equation (1) shown in the first embodiment is used, the permeation amount of hydrogen gas permeating the electrolyte membrane is estimated by obtaining the difference in leak amount at two different time points within the standard pressurization time tn. Is possible.

  FIG. 4 is an explanatory diagram showing a method for estimating the hydrogen gas permeation amount. FIG. 4A shows the time change of the hydrogen flow rate measured by the hydrogen flow meter 300, and FIG. 4B shows the time change of the hydrogen pressure detected by the pressure sensor 330 of the low pressure part LS.

The gas permeation amount Q _t through the electrolyte membrane increases in proportion to the hydrogen partial pressure in the anode. That is, the gas permeation amount _Qt and the pressure P in the anode (= pressure of the low pressure part LS) have the following relationship. Where ε is the gas permeability and S is the area of the electrolyte membrane.

Q _t = ε · P · S

When the leak amount Q _leak is calculated using the above equation (1) at the time points t1 and t2 shown in FIG. 4B, a difference ΔQ _t occurs in the _leak amount Q _leak . Since this ΔQ _t is a difference due to the permeation of gas through the electrolyte membrane, the leakage amount Q _leak at time points t1 and t2 is expressed as (leakage amount t1) and (leakage amount t2). The amount of gas produced can be expressed as follows.

ΔQ _t = (leakage amount t1) − (leakage amount t2)
ΔQ _t = (ε · P1 · S) − (ε · P2 · S)
That is,
ΔQ _t = ε ・ ΔP ・ S

  Since S is a predetermined value and ΔP can be measured by a pressure sensor, the gas permeability ε can be estimated from this equation. Therefore, by using this gas permeability ε, it is possible to estimate the amount of hydrogen gas that permeates the electrolyte membrane as shown by the broken line in FIG. Further, the degree of deterioration of the electrolyte membrane can be estimated from the magnitude of the gas permeability ε.

For example, if the hydrogen gas permeation amount estimated by the above-described method is used, the leakage amount of hydrogen gas during power generation of the fuel cell 10 can be accurately estimated. The leakage amount Q _leak in such a case can be obtained by the following equation.

Q _leak = Q _flow -((hydrogen consumption estimated from output current of fuel cell) + (hydrogen amount purged from purge valve 240) + (hydrogen gas permeation amount))

(Modification 2)
In the first and second embodiments described above, it is possible to detect abnormalities such as hydrogen leaks and component failures occurring in the hydrogen system. On the other hand, by using the shut valve 250 indicated by a broken line in FIG. As shown in FIG. 1, the shut valve 250 is provided between the second pressure regulating valve 220 and the hydrogen flow meter 300.

  FIG. 5 is a timing chart when the abnormality detection process is executed step by step using the shut valve 250. First, when the control computer 400 opens the on-off valve 200 with the shut valve 250 closed, hydrogen gas is supplied to the upstream portion of the shut valve 250. Then, as shown in the figure, the hydrogen flow meter 300 detects the flow rate of hydrogen flowing into the intermediate pressure part MS, and the pressure sensor 320 detects the pressure increase in the intermediate pressure part MS. If the abnormality detection process shown in FIG. 2 or FIG. 3 is executed during this period, it is possible to detect hydrogen leakage or component failure that occurs downstream from the on-off valve 200 and upstream from the shut valve 250. .

  If no hydrogen leak or component failure is detected by the first abnormality detection process described above, the control computer 400 opens the shut valve 250. Then, since hydrogen is supplied downstream from the shut valve 250, the flow rate flowing into the low pressure part LS is detected by the hydrogen flow meter 300, and the pressure increase in the low pressure part LS is detected by the pressure sensor 330. If the control computer 400 executes the second abnormality detection process in such a period, the control computer 400 can detect hydrogen leakage or component failure that has occurred on the downstream side of the shut valve 250.

  As described above, according to this modification, a shut valve is provided in the hydrogen supply flow path 24, and the shut valve is opened in stages, so that a site where hydrogen leakage or component failure has occurred can be detected. It becomes possible to detect according to the position of the shut valve. In addition, in this modification, although the example which has arrange | positioned only one shut valve was shown, there is no restriction | limiting in the number. When a plurality of shut valves are provided, the shut valves are opened sequentially from the upstream side of the hydrogen supply flow path 24. Then, hydrogen leakage or the like is detected in a section located immediately downstream of the opened shut valve, and when the detection ends, the next shut valve is opened and the same process is repeated. Thus, if the abnormality detection process is repeatedly executed using a plurality of shut valves, the position of the abnormality occurrence can be accurately specified.

(Modification 3)
In the first embodiment and the second embodiment, one hydrogen flow meter 300 is used to detect abnormality of the entire hydrogen supply flow path 24. In contrast, by disposing a hydrogen flow meter at each pressure part in the hydrogen supply flow path 24, it is possible to detect hydrogen leakage and component failure for each pressure part.

  FIG. 6 is an explanatory diagram showing the overall configuration of the fuel cell system 100 in the present modification. As shown in the figure, the present modification employs a configuration in which a hydrogen flow meter 301 is added to the high-pressure part HS and a hydrogen flow meter 302 is added to the low-pressure part LS with respect to the fuel cell system 100 shown in FIG.

  In the fuel cell system having such a configuration, the control computer 400 performs the abnormality detection process shown in FIG. 2 or FIG. By doing so, it is possible to detect hydrogen leakage or component failure in each pressure part. That is, the location where the abnormality has occurred can be specified in the same manner as in the second modification described above. Further, in this modification, the process of opening the shut valve in stages as in Modification 2 described above is not necessary, so that the location where an abnormality has occurred can be detected more quickly.

(Modification 4)
When supplying hydrogen gas to the fuel cell 10, a large pressure loss may occur due to the anode flow path in the fuel cell 10. Therefore, in the above-described abnormality detection process, hydrogen gas is supplied from the anode outlet of the fuel cell 10 together with the opening of the opening / closing valve 200 (steps S210 and S410), thereby equalizing the hydrogen pressure. It is possible to improve the accuracy of abnormality detection.

  For example, if the circulation device 70 is constituted by an ejector, the opening degree of the ejector is fully opened and the primary pressure of the ejector is gradually increased. By doing so, the circulation capacity of the circulation device 70 can be suppressed, so that hydrogen flows backward through the anode off-gas flow path 26, and hydrogen gas can be supplied also to the anode outlet side.

  Further, if the circulation device 70 is constituted by a hydrogen pump, by rotating the hydrogen pump in the reverse direction, the hydrogen gas can flow back to the hydrogen circulation flow path 28 side and the hydrogen gas can be supplied to the anode outlet.

  In addition to supplying hydrogen gas to the anode outlet using the circulation device 70, a dedicated channel for supplying hydrogen gas to the anode outlet may be separately provided.

  FIG. 7 and FIG. 8 are explanatory views showing an example of a dedicated channel for supplying hydrogen gas to the anode outlet. In the fuel cell system 100 shown in FIG. 7, the vicinity of the anode inlet of the hydrogen supply channel 24 and the vicinity of the anode outlet of the cathode offgas channel 36 are connected by a bypass channel 37, and a shut valve is placed in the bypass channel 37. 38 is provided. The control computer 400 can supply hydrogen gas also to the anode outlet side by opening the shut valve 38 when the abnormality detection process is started. At the end of the abnormality detection process, the shut valve 38 is closed.

  On the other hand, in the fuel cell system 100 shown in FIG. 8, a three-way valve 39 is provided in the vicinity of the anode inlet of the hydrogen supply channel 24, and hydrogen gas is supplied to the anode inlet and the anode outlet of the fuel cell 10 with respect to the three-way valve 39. The flow path 41 to be introduced is connected. Even in such a configuration, the hydrogen gas can be supplied to the anode outlet of the fuel cell 10 by controlling the three-way valve 39 simultaneously with the execution of the abnormality detection process.

(Modification 5)
In the above-described embodiments and modifications, the flow rate of hydrogen supplied to the hydrogen supply flow path 24 is measured by the hydrogen flow meter 300. However, the flow rate may be estimated by various methods without using the hydrogen flow meter 300. it can. For example, the flow rate of the hydrogen gas supplied to the hydrogen supply flow path 24 can be estimated by measuring the pressure change of the hydrogen gas immediately after being supplied from the hydrogen tank 20. Further, the hydrogen flow rate can also be estimated from the differential pressure generated before and after a component (for example, the first pressure regulating valve) arranged immediately after the hydrogen tank 20.

(Modification 6)
The operation mode setting in steps S300, S330, and 310 of the abnormality detection process shown in FIG. 2 is performed by referring to a predetermined operation mode table in which the operation mode is defined according to the presence or absence of hydrogen leakage and the presence or absence of failure. It may be a thing. FIG. 9 shows an example of the operation mode table. In the illustrated example, the operation mode is defined only for the presence or absence of a hydrogen leak and the presence or absence of a failure. For example, the operation mode may be defined depending on the location of occurrence of a hydrogen leak or the location of a failure. Good. By using such a table, the operation mode can be set in detail according to the presence or absence of hydrogen leakage or the presence or absence of failure.

It is explanatory drawing which shows the whole structure of the fuel cell system 100 as 1st Example. It is a flowchart of the abnormality detection process in 1st Example. It is a flowchart of the abnormality detection process in 2nd Example. It is explanatory drawing which shows the estimation method of hydrogen gas permeation | transmission amount. 4 is a timing chart when executing abnormality detection processing step by step using a shut valve 250; FIG. 10 is an explanatory diagram showing an overall configuration of a fuel cell system 100 in Modification 3. It is explanatory drawing which shows the example which provided separately the flow path for supplying hydrogen gas to an anode exit. It is explanatory drawing which shows the example which provided separately the flow path for supplying hydrogen gas to an anode exit. It is explanatory drawing which shows an example of an operation mode table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 20 ... Hydrogen tank 24 ... Hydrogen supply flow path 26 ... Anode off gas flow path 28 ... Hydrogen circulation flow path 30 ... Blower 34 ... Air supply flow path 36 ... Cathode off gas flow path 37 ... Bypass flow path 38 ... Shut valve DESCRIPTION OF SYMBOLS 39 ... Three-way valve 40 ... Secondary battery 50 ... Motor 55 ... Axle 60 ... Gas-liquid separator 70 ... Circulating device 90 ... Vehicle 100 ... Fuel cell system 200 ... On-off valve 210 ... First pressure regulating valve 220 ... Second pressure regulating valve 240 ... Purge valve 250 ... Shut valve 300,301,302 ... Hydrogen flow meter 310-330 ... Pressure sensor 400 ... Control computer

Claims (12)

A fuel cell system for generating electricity by supplying hydrogen and oxygen to a fuel cell,
Hydrogen supply means for supplying the hydrogen to the fuel cell;
A hydrogen supply flow path connecting the hydrogen supply means and the fuel cell;
A flow rate detection means provided in the hydrogen supply flow path for detecting the flow rate of hydrogen supplied from the hydrogen supply means to the fuel cell;
State quantity detection means provided in the hydrogen supply flow path for detecting at least one of the state quantities of hydrogen supplied to the fuel cell;
A pressurization period before the start of power generation by the fuel cell and until the pressure in the hydrogen supply flow path reaches a predetermined pressure suitable for power generation of the fuel cell from the start of supply of hydrogen by the hydrogen supply means The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel cell is calculated based on the hydrogen state quantity detected by the state quantity detection unit, and the calculated flow rate and the flow rate detection unit detect A leakage detection unit that detects leakage of the hydrogen based on the flow rate ,
The leak detection unit is a fuel cell system that detects the leak during at least a part of the pressurization period until pressurization ends . The fuel cell system according to claim 1 ,
The leak detection unit detects the leak based on a change in the hydrogen state quantity in the partial period. The fuel cell system according to claim 1 ,
The state quantity detection means comprises means for detecting the pressure of hydrogen supplied to the fuel cell,
The leak detection unit obtains an average pressure of the hydrogen in the partial period, and calculates the leak amount of hydrogen calculated in the partial period based on the average pressure at the time of completion of the pressurization period. Fuel cell system that compensates for quantity. The fuel cell system according to any one of claims 1 to 3 ,
The hydrogen leakage amount is calculated based on the calculated flow rate and the flow rate detected by the flow rate detection means at two different time points within the partial period, and a difference between the leakage amounts at the two time points is calculated. And a permeation amount estimation unit for estimating a permeation amount of hydrogen permeating from the anode to the cathode through the electrolyte membrane in the fuel cell. A fuel cell system for generating electricity by supplying hydrogen and oxygen to a fuel cell,
Hydrogen supply means for supplying the hydrogen to the fuel cell;
A hydrogen supply flow path connecting the hydrogen supply means and the fuel cell;
A flow rate detection means provided in the hydrogen supply flow path for detecting the flow rate of hydrogen supplied from the hydrogen supply means to the fuel cell;
State quantity detection means provided in the hydrogen supply flow path for detecting at least one of the state quantities of hydrogen supplied to the fuel cell;
A pressurization period before the start of power generation by the fuel cell and until the pressure in the hydrogen supply flow path reaches a predetermined pressure suitable for power generation of the fuel cell from the start of supply of hydrogen by the hydrogen supply means The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel cell is calculated based on the hydrogen state quantity detected by the state quantity detection unit, and the calculated flow rate and the flow rate detection unit detect A leakage detection unit that detects leakage of the hydrogen based on the flow rate,
The fuel cell is connected to an anode off gas flow path for discharging the anode off gas,
The anode off gas channel is connected to the hydrogen supply channel via a circulation device for circulating the anode off gas to the hydrogen supply channel,
A fuel cell system comprising means for controlling the circulation device during the pressurization period to supply the hydrogen supplied from the hydrogen supply means in a reverse flow to the anode off-gas flow path. A fuel cell system according to any one of claims 1 to 5 ,
In the hydrogen supply channel, at least one shut valve is provided between the flow rate detecting means and the fuel cell,
The state quantity detection means is provided for each section in the hydrogen supply flow path partitioned by the shut valve,
Each shut valve is closed in the initial state,
The leak detector is
Means for sequentially opening the shut valve from a shut valve provided on the flow rate detecting means side toward a shut valve provided on the fuel cell side;
The state quantity provided in a section located between the opened shut valve and an unopened shut valve or the nearest one of the fuel cells located on the fuel cell side of the opened shut valve The state quantity of the hydrogen in the section is detected by the detection means, the flow rate of hydrogen supplied from the hydrogen supply means to the section is calculated based on the state quantity, and the calculated flow rate and the flow rate are calculated. A fuel cell system comprising: means for detecting leakage of hydrogen in the section based on the flow rate detected by the detection means. A fuel cell system according to any one of claims 1 to 5 ,
The hydrogen supply channel includes at least one pressure regulating valve;
The state quantity detection means and the flow rate detection means are provided for each section in the hydrogen supply flow path partitioned by the pressure regulating valve,
The leak detection unit detects the leak for each of the sections. The fuel cell system according to any one of claims 1 to 7 ,
Furthermore, a pressure regulating valve for adjusting the pressure of hydrogen supplied from the hydrogen supply means is provided between the state quantity detection means and the hydrogen supply means in the hydrogen supply flow path,
The state quantity detection means comprises means for detecting the pressure of hydrogen supplied to the fuel cell,
When the leak is not detected by the leak detection means, the pressure regulating valve fails when the hydrogen pressure detected by the state quantity detection means is lower than a predetermined pressure suitable for power generation of the fuel cell. A fuel cell system comprising a failure determination unit that determines that the failure has occurred. The fuel cell system according to claim 8 , wherein
The fuel cell system is mounted on a vehicle,
A fuel cell system, comprising: an operation mode setting unit that sets an operation mode of the vehicle according to at least one of a leak detection result by the leak detection unit and a failure determination result by the failure determination unit. The fuel cell system according to claim 9 , wherein
The operation mode setting unit prohibits power generation by the fuel cell and travel by a secondary battery provided in the vehicle when the leak is detected by the leak detection unit. Fuel cell system set to secondary battery operation mode. The fuel cell system according to claim 9 or 10 , wherein
The operation mode setting unit sets the operation mode to a limp-form operation mode that allows traveling while limiting output to the fuel cell when the failure determination unit determines that a failure has occurred. Fuel cell system. In a fuel cell system for generating power by supplying hydrogen and oxygen to a fuel cell, a hydrogen leak detection method for detecting hydrogen leak,
The fuel cell system is provided in the hydrogen supply channel, a hydrogen supply unit that supplies the hydrogen to the fuel cell, a hydrogen supply channel that connects the hydrogen supply unit and the fuel cell, and the hydrogen supply channel A flow rate detection means for detecting a flow rate of hydrogen supplied from the supply means to the fuel cell; and a state in which at least one of the state quantities of hydrogen supplied to the fuel cell is provided in the hydrogen supply flow path A quantity detecting means,
A pressurization period before the start of power generation by the fuel cell and until the pressure in the hydrogen supply flow path reaches a predetermined pressure suitable for power generation of the fuel cell from the start of supply of hydrogen by the hydrogen supply means The flow rate of hydrogen supplied from the hydrogen supply unit to the fuel cell is calculated based on the hydrogen state quantity detected by the state quantity detection unit, and the calculated flow rate and the flow rate detection unit detect And a detection step of detecting leakage of the hydrogen based on the measured flow rate ,
In the detection step, a hydrogen leak detection method for detecting the leak in at least a part of the pressurization period until pressurization is completed .

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